IMPERIAL AGRICULTURAL
RESEARCH INSTITUTE, NEW DELl-H,
1C)'3Sh
rrUE lYIA.lOR SOIL :n [VISIONS
Olr
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UNrl':ljjl) ti r.J1A ~l']~S
PEDOLOCIC ROYALTY-AN AMEHICAN BLACK]W'l']1
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THE MAJOR SOIL DIVISIONS
O]T THE UNITED STATES
A PEDOLOGIC-GEOGRAPHIC SURVEY
BY
IAJUIS A. W01,},'ANGER, PH.D.
Economic alld Soil Gcuympltcr.
(/ab'7IIbia
Uni'Jc'I'sity
Parml'rlll Soil Saintti.v/, ]Jllrrrllt of ()hl'mi,~l"y
"nd Soils, Unitl'd SlrJI<'s Dcpf!'l'tment
qf A!}I'I'w/lltre
NEW YOm(
JOHN WILEY & SONS,
J"ON"lHlN:
CHAPMAN & HALL,
1930
19986
1IIIIlllI11111~llII111~11111111i1
IARI
INC.
LIMI'I'EI)
COPYRIGHT,1980
DY
LOUIS ALBJmT WOLl!'ANGER
Printed in
u. S. A.
PRESS OF
ElRAUNWORTH 8.
co.,
'NC.
900t( MANl.IFACTL,1REE:FlS
OROOl<LYN. ND:W VORK
To
MY MOTHER
CLARA HENNINGER
AND
MY WIFE
lIENIUE'J.'TA U. RODEMANN
PREFACE
The soil of the United States has long been recognized as one of its more important resources, yet
geographic inquiries relating to the soils of the
country as a whole have been almost wholly neglected. Valuable studies of various types covering
selected areas ranging from a few square miles
through counties/ states,2 major natural regions,n
and large sections of the republic 4, have been made,
but the restricted nature precludes the offering of
a perspective survey of the soils in their entirety.
In fact, the literature does not reveal a single wor!\:
devoted wholly and primarily to the subject. Limited references bearing on this theme may be found
scattered here and there through treatises and
papers concerned with other aspects of soils and
geography but the ideas expressed and the conclusions drawn are in most cases incidental and either
local or very general in character.
J. Soil Sur"Voy Repo~·ta and Maps, U. S. Department of Agriculture,
Field Opemtiona of tho Bureau of Soils, 1899-1924 (Annual
Reports).
2 Soils of Wiscollsin, Wis. Geol. and Nat. IIist. Survey, et aI.
S C. F. Marbut: Boils of the Great Plaina, Annals Assn. Amer.
Googrl3., Vol. XIII, No.2, 1923, et al.
• II. II. Bennett: The Soil and Agriculture of the Southern States,
et nl.
ix
x
PREFAOE
Aside from the widespread and dominating interest in other fields of geography, particularly l)hysiography and climate, the lack of attention to the more
comprehensive study in soil geography may be
largely ascribed to the general misunderstanding,
holding until recently, as to the true nature of soils
and their real significance, and to the bolief that
soils were chiefly local phenomena. Soils woro assumed to have properties which they did not POSROSS,
and the more significant features they did possess
were practically unknown. Since the bulk of the
material from which soils are formed is derived
from geologic formations, it has long been held
and is still widely believed that the characteristics
of the soils correspond closely with the properties
of these materials, that is, soils formed from limostones were regarded as rich and limey, those from
shale, impoverished and acid, etc. In short, as the
rock, so the soil. This being held true, and geologic
formations varying widely over comparatively smull
areas, it was likewise assumed that soils were but
local entities whose basic features changed with the
underlying formations. Under these circumstances,
a soil map of the United States was in effect no more
than a complex geologic map slightly modified to
express textural inequalities, so intricate and 80
lacking a broad common denominator as to dissuade
the investigator from seeking the soils' collective
geographic relationships.
The studies of recent years, however, on the part
of pedologists both in this country and abroad have
given rise to an entIrely new philosophy with regard
PREFACE
xi
to soil attributes, soil definition and soil distribution. G Discarding or subordinating the genetic interpretation-long adhered to but oddly not recognized as aecidedly limiting to thcir work-and giving their first attention to the fundamental properties of the soils themselves irrespective of their
origin, pedologists are now agreed that the basic
characteristics of normal soils are not in accord with
their parent materials 6 but are largely determined
by the climatc and vegetation under which the soils
evolve and by the land form they occupy.7 In other
words, given a type of soil-forming material, the
forces and factors operating on that material, rather
than the material itself, are of prime importance in
governing the resultant soils' fundamental properties-a most revolutionary departure from the timehonored and widely held genetic interpretation.
Moreover, it has been brought out that soils are of
regional as well as local importance, and like land
forms,s natural vegetation,1l climate,Jo etc., may be
classified into large and comprehensive groups of
small number. The soils composing such a group
differ considerably in local detail but their basic
attributes over extensive areas are nevertheless
essentially alike.
Ii II. L. Shant?; and C. F. Marbut: The Vegetation and Solls of
Africa, Amer. Googr. Soc. Resoarah Ser. 13, 1923, pp. 115-121.
"Ibid., pp. 120-121.
1 IDid., pp. 119-120.
6 N. M. Fenlleman: Physiographic Divisions ot the United States,
Annals Assn. Amer. Geogrs., Vol. XVIII, pp. 261-353.
D H. L. Shantz and R. Zon: Natural Vegetation, Atlas of Amer.
Agr., Part I, Sea, E.
10 R. D. Ward: The Climates of the United States.
xii
PREFACE
It is the object of this study to examine the largest
of such groups which may be recognized in the
United States-the major soil divisions; to set rorth
their fundamental functional characteristics, and to
determine some of their essential and more important geographic relationships. Industries in
which the soils in general show their more hnmediate relationships have been selected for analysis.
The distribution of each with reference to tho groat
soil divisions will be observed, and the essential features governing their association noted. A specHic
aim has been that of basing all considerations upon
the present-day soil point of view, and on those Mil
features more easily comprehended by the general
reader.
In view of the youth of modern soil science and
the paucity of literature summarizing its principles
and philosophy, the author has deemed it expedient
to include a brief sketch of the more important soilforming elements and their bearing upon the soils'
characteristics, in addition to the description or the
soil groups. As it is obviously impossible to compact such a discussion within a few pages, the treatment is considerably abbreviated. It aims to present only material that is believed to be of prime
interest in interpreting the geographic relationships
thereafter set forth.
For a large part of the soil data and conclusions
employed in this study, the writer is indebted to his
many soil colleagues and co-workers whose enormous labors have been engaged in the study and interpretation of the hundreds of soils of the United
PREFACE
xiii
States, in both field and laboratory. Without the
impetus given to the matter of establishing soil
units, the location of their boundaries on the ground,
the representation of these boundaries 011 maps, and
the extensive studies of soils in the field on the part
of Dr. Milton Whitney and his associates, the detailed knowledge available on the soils would be
seriously limitod.
In pursuing this study, the author is particularly
indebted to Dr. Curtis F. Marbut, whose stimulating
suggestions through years of friendly conference
and discussion in field and office have been of invaluable aid. His keen perception and skillful application of the philosophy and principles of modern soil
science have firmly established the foundation upon
which many of the future important soil studies,
both in this country and abroad, will undoubtedly
rest.
'1'ho author recalls with gratitude the inspirational
guidance of his first teacher, Dr. Nels A. Bengtson,
of the University of Nebraska, who laid the foundation for his work in geography and soils, and the
generous assistance of his university associates,
Doctors J. Russell Smith, Charles P. Berkey,
Douglas W. Johnson, John E. Orchard and O. S.
Morgan, who have followed his work with encouragement and many helpful criticisms.
LOUIS
COr,UMIHA. UNIVERSITY, NlllW' YonE: CITY,
May 1, 1929.
A.
WOLFANG:ER.
CONTENTS
CHAPTER
I
PAGE
MAJOR SOIL DIVISIONS AND THEIR GEOGRAPHIC QUA:LIFICATIONS
1
1
CLASSIFICA'l'ORY CRITERIA
a
THm GENE'rIC SYSTEM
GEOLOGIC CLASSES
4
Thoory of Soils and Gcologic Formations
Discordance betwoen Soils and Geologio Formations
CLIMA'rIC CLASSES .
BOTANIC AND TOPOGRAPHIC CLASSES
4
.5
7
8
I)
Tmll A'l'TRIDU'l'IVE SYSTEM
CrmOMATIC CLASSES
9
TEXTURAL CLASSFlS
10
11
MATURATAL CLASSES
The Pedologic Cycle
Mature Soils
Young Soils
Old Soils .
11
11
OTHER PHYSICAL CLASSES
CHEMICAL CLASSES
Limo-accumulat.ing and Non-lime-accumulating Soils
Geographic Attributes .
N omenelature
The Problem of Variation
THE GREAT SOIL GROUPS
THrn PEDALFmRIC Guoups.
The Podsols .
The Gl'ay-Brownerths
The Rcd-and-Yellowerths
The FerruginouB Laterites
The Prairyerths .
THE PmDOCALIC
12
13
14
14
14
15
16
16
18
18
20
21
24
25
26
Gaoups
27
The Blackerths
28
xv
xvi
CONTENTS
PAGE
29
30
The Chestnuterths
The Bt'ownerths .
The Grayerths
31
31
ROUGa: BltoRJllN LAND
CIIAPTEH, II
34
THE PEDALFlllRS •
THE PEDALFEIUC ENVlRONMEN"T
35
35
CLIMATE.
31i
Precipitation •
Temperature .
37
38
39
NATUIl,AL VEOETA'1'ION •
PARENT MA'l'ERIALS
LAND FORMS
THE MICRO-FLORA AND TilE SOIL l?AUNA
SIGNIFICANT CHARAC'rElRIS'1'ICS
42
44
.
CHEMICAL PnOPER'l'IElS.
Broad Effect of Climate lIud V('getatiou
The Chemical Profile
The Chemical Impoverishment.
PHYSICAL CHARACTERISTIOS
41
•
Texture Profile
Disadvantages ()f the Textural Profile
Advantages of the 'l'extural Profile
Structure Profile .
Significance of Strueture .
Evaluation of the SLructure Profile
Color Profile .
TnE PRAIRYl!JRTHS
THE CON'l'RAST WITH THE LIGHT COLORED PEDALT"EItS
44
44
45
48
49
50
511
51
52
53
54
55
57
57
THE CLIMATIC, G:EOLOGIC AND 'rOl'O(lUAl'IIIC ENVIlWNMElNT
58
THE NATUUAL VEGETATION
59
•
Prail'ie Gmsses
Relationship of the Prairyertha to the Pedalfers
THE WEB'l.'EltN PEDALFIilRB
•
59
60
61
xvii
CONTENTS
CHAPTER
III
PAGE
63
63
63
63
64
65
66
67
68
68
68
69
TilE PEDOCALS
Turn PI!lDOCALIC ENVIRONMJilNT .
CLIMA'rE •
Precipitation .
Temperature .
NATURAL VEGETATION.
P AltENT MA'l'ERIALS
LAND FOUMS
SIGNIFlCAN'l' CUAUAC'l'ElURTWB
CHIOMICAL PROPEH'I'IIilS.
Broad Effect. uf Climate and Vegetation
Chemical Profile .
74
74
PUYSICAL PnOPERTIES .
Texture Pl'Ofile
Structure Profile
Color Profile .
75
.
77
79
MINon PEDOCALIC BIoJLTS
CHAPTER IV
80
GEOGRAPHIC RELATIONSHIPS
Gl!lNElltAL PmNCIPlJES
HUMAN AC'l'IVITIElS DEPENDING UPON TUID SOIL
80
80
81
AREAT. COltRELATlONS •
•
SOIL VS. CLIMATln, LAND FORMS AND NA'l'URAL VEGETATION
AGRICULTURAL ADJUSTMENTS
LAND UNDIDR CULTIVATION
The Major Soil Divisions
83
86
Status of Cultivated Land in the Two Divisions
Relationship of Pedalfers to I... and under Cultivation
Relationship of Pedocals to Land under CUltivation
The Great Soil Groups
The I'edalfers
The Pedoeals .
PRINCIPAL Cnops
The Major Soil
•
Divisions
The Great Soil Groups .
The Prairyerths
The Gray-BrowIlcrths
86
87
87
88
92
94
94
97
98
100
101
• 102
105
xviii
CONTENTS
:PAGE
108
The Red-and-Yellowerths
The Ferruginous Laterites
The Podsols
The Blackerths
The ChestnuterLhs
The Brownerths and Grayerths
Summary of Pedologic Relationships
PASTORAL ADJUSTMENTS
DISTRIBUTION OF P ABTORALISM
RELATIONBIIlPB
UO
112
112
118
119
1l!J
120
0
120
0
121
121
0
Pastoralism, Grasslands anci Soils
The Major Soil Divisions
The Great Soil Groups
122
12<1
12G
12G
127
127
0
N EMORICULTURAL
ADJUSTMENTS
DISTRIBUTION OF NEMORICULTURE
RELATIONSHIPS
0
The Major Soil Divisions
The Great Soil Groups
128
SUMMARY AND CO]'fCLUBION
131
BIBLIOGRAPHY
13li
INDEX
141
TABLES
Io
II.
III.
IV.
PERCENTAGE OF MATURE SOILS IN SELECTED COUNTIES
CHEMICAL ANALYSES OF REPRESENTATIVE MATURlil PEDALFERB
CIlEMICAL ANALYSES OF REl'RESJoJNTA'i'IVE MA'J~UIl.JoJ PEDOGALS
RELATIVE RANK OF PEDALFERIC GREAT SOIL GROUPS
43
47
71
AccmtDSon,
ING TO PROPORTION OF LAND UNDER CULTrvA'rION AND
AND CLIMATE FAVORABILITY
V.
VI.
•
POTATO YIELDS ON SEVERAL FLORIDA SOITJS •
95
III
FERTILIZER EXPENDED TO PRODUCE ONE BUSIIEL OF POTATOES,
1925
112
MAJOR SOIL DIVISIONS AND GREA'r SOIL
GROUPS OF. THE UNITED STATES
Boundaries are generalized and all local features,
such as the numerous but relatively inextensive areas
of rough stony land in the grayerth region and elsewhere, are omitted.
Each region shown includes soils in all stages of
development but thoy cannot be differentiated owing
to theu' intimate association and the scale of the
map, 118 well as incomplete knowledge with reference
to their actual distribution. Tho mature soils, the
age group under chief considerution in this study.
may be interpreted in general as mantling all smooth
well drained surfaces (see pages 11-13, 19-20).
'rho proportion of such soils is necessarily relatively
low in the mountain and hill areas and high in the
plain and plateau areas.
The writer is indebted to the Bureau of Chemistry and Soils for permission to use the unpublished
soil map of the United States, prepared by the Soil
Survey, for a part of the data employed in the
prtJparation of this map.
THE MAJOR SOIL DIVISIONS
OF THE UNITED STATES
,A, PEDOLOGIC-GEOGRAPHIC SURVEY
CHAPTER I
MAJOR SOIL DIVISIONS AND THEIR GEOGRAPHIC
QUALIFIOATIONS
CLASSIFICATORY ORITERIA
The enormous diversity in the soils of the United
States immediately confronts the investigator, who
seeks to study their geographic relationships as a
whole, with the subject of classification. Over 1500
soil series or kinds of soils, irrespective of textural
differences, have to date been identified.]. This list
is so large that even the soil specialist has difficulty
in bearing in mind the peculiar features of each.
And as time goes on, at least several hundred more
of various degrees of importance will undoubtedly
be added to the sum. How may this large number
be classified and what are the essential characteristics of the soils of each division?
1 C. F. Shaw: The Soil Series Names, Amer. Soil Survey Assn.,
Bull. X, pp. 85-101.
2
MAJOR SOIL DIVISIONS
The simplest classification would obviously be ono
in which the soils could be embodi.ed in ona of several, preferably two, contrastive groups. Such an
inclusion would ba analogous to the geologists' division of the earth into atmosphere, hydrosphere
and lithosphere, the geographers' differentiation of
land forms as plains-plateaus and hills-mollutains,
or the climatologists' separation of elimates into arid
and htunid. The basis upon which each of these
divisions is effected is relatively simple, for numerous objects do not have a great number of features
in common but each group is clear cut and is fundamentally unlike the others in many important respects and relationships.
Fortunately, soil students and otherfl int~rCAtcd
in this element of the natural environment have
given much thought to the problem of classification,
and numerous schemes have been pl'oposed. 2 They
are based upon various considerations. Although
there are many points of view, they may chiefly be
regarded as members of one of two systcmR: (1) the
genetic, in which tho relationships of the factors producing the soil are employed as criteria, and (2) tho
attributive, in which the soils' own attributes or features serve as the basis.
In examining any member of ono of these systems
with the hope of employment ill this study, its serviceability must be judged by several qualifications.
In the first place, the disposure should bring out tho
soils' own characteristics. Because it is the object
2 C. F. Marbut: A Scheme for Soil Olassification, Proe. and Papers
First Int'l. Congo Soil SeL, Com. V, 1927, pp. 1~31.
THE GENETIC SYSTEM
:3
of this work to ascertain the essential relationships
between the soils and certain types of human activity, such relationships can be established only when
the features of the soils themselves, and not those
of factors outside the soils, are first considered. In
the second place, in view of the scope of this study,
these characteristics should be fundamental, and not
accidental or subsidiary. Third, in order that there
may be accordance within the group, the characteristics must be in harmony with other features of tho
soils. Fourth, the characteristics must be those of
the greatest universality, because only a few broad
inclusive groups are desired and a large number of
soils have few accordant fundamental features in
common.
TIlE GENETIC SYSTEM
When, in the latter part of the nineteenth century,
scientific interest in the soils of the United States
received its first general impetus through the efforts
of Milton Whitney, E. W. Hilgard and other workers, the true nature of these natural bodies was essentially unknown. Although long utilized by man,
continuously underfoot, very readily accessible, and
a vital factor in the settlement and colonization of
the nation, the soil had, previously to this period,
received but scant systematic scientific attention.
Whatever interest it had evoked had been largely
in the direction of bringing about modifications in
its character rather than a thorough understanding
of this character.
4
MAJOR SOIL DIVISIONS
GEOLOGIC OLASSES
Theory of Soils and Geologic Formations.-Lacking facts, philosophy and principles of their own,
and seeking guidance in the maiter of deillling, classifying and interpreting the objects of their stndy,
the early investigators turned naturally to related
sciences the workers in which had suggested relationships between their phellomena aIHl the soil.
The trend was particularly ioward geology, because
its interpretations, without discriminative analysis,
appeared to be well founn('d. "GC'ologists, as the
science developed during the 19th century, had assumed that, since soils lie on the earth's snrrace and
are made up mainly of mjneral particles, therefore
soil units aTe equivalent to gC'ologic Ullits and the
relationships of soils or widely spparat('n arcas are
the same as the relationships oj' the geologic formations in these areas." 3 The same or similar limestones or sandstones, for example, were supposed to
yield soils of like corresponding character. No geol~
ogist in the United States is known to have made
an attempt to "establish this assumption as a fact
through the study of ihe soil itself further than to
make some general texture comparisons," 4 but i i
supplied an initial basis, presumedly scientifically
sound, upon which the soil students could define and
group their soils. They accepted the postulation
because there was no other of equally apparent
merit.
8 Ibid., pp. 2-3.
"Ibid., p. 3.
THE GENETIC SYSTEM
5
Employing this interpretation, soil students defined soils as "weathered products" and divided
them into two major groups in which the divisions
were designated as "residual" and" transported."
The former was then further subdivided in accordance with the rocks giving rise to the accumulations
formed in situ (limestone, sandstone, etc.) and the
latter in accordance with the forces which had transferred the deposits (glacial, eolian, etc.). The system was not confined to this country but was widely
used abroad. It furnished the chief basis for the
well-known official studies and soil map of the Bureau of Soils published as Bulletin 96, in 1913,6 and
the earlier work of G. N. Coffey in 1911.°
Discordance between Soils and Geologic Formations.-With increasing study it became evident,
however, that the basic features of normal soils are,
with unimportant exceptions, not determined by
their parent material. More careful examinations
of the soils and comparisons of their features
began to show that soils derived from the same
or similar parent materials are not consistently
alike. rrhey also brought out the fact that
soils derived from dissimilar materials are in many
cases fundamentally alike. To illustrate, the rich
loess-like formations of Mississippi give rise to
thoroughly leached, light colored soils, low in organic matter and with coarse-nutty structured subr, C. F. Marbut, at al.: Soils of the United States, Bun. 96, Bur.
'Soils, U. S. Dept. Agr., 1913.
() G. N. Coffey: A Study of the Soils of the United States, Bull.
85, Bur. SoilS, U. S. Dept. Agl'., 1912.
6
MAJOR SOIL DIVISIONS
soils, whereas those of south central Nebraska form
comparatively unleached, almost black soils, high in
organic matter and with fine-granular Htrnctures in
both surface and subsoi1:/ On tho other hand, the
normal soils del'ivcd from formations vat'ying from
those of the driftless areas of vVi::;eonHill, through
the highly <lalcarcous glacial till of the {,Jower Lake
states, to the crystalline rocks of tho Maryland Piodmont and the relatively Ullcol1solidat('(l Coastal
Plain deposits are essentially alike. They are light
in color, relativoly moderately leaclwd, low in organic matter, have light t(~xtnred, simple structured
surface horizons and relatively heavy textured,
nutty structured subsoils, and POH8CSS the sarno
basic chemical features. 8 In short, "it was founel to
be wholly impossible to harmonize fundamental soil
characteristics with geologic characterisHc8 on any
other basis than the complete independence oI the
one from the other group of characteristics." 0
If this discordance is true, and the conclusion is
now apparent to everyonc who carefully examines
the facts, it is evident that definitions and groups
based upon geologic derivations reveal nothing of
importance about the .fundamental natl1ro of the
soils and are thorofore of no value in making the
geographic studies here propoHed. They take no
cognizancc or the properties of the soils, but classify
merely, in the case or "residual" and "trans~
7 U. S. Dept. Agr., Field Operations, Bureau of Soils, 1915, pp.
1008-1011 j ] 924, pp. 20-24.
8 Ibid., 1921, p. xv.
Il C. F. Marbut: A Behomo for Soil Clnssification, op. cit., p. 4.
THE GENETIC SYSTEM
7
ported," the methods by means of which the materials from which the soils were evolved are accumulated and, in the case of the" limestone" and" sandstone" groups, the soils in accordance with the rocks
from which the original soil-forming mineral matter
was derived. Relationships established on the basis
of such groups are geologic, not pedologic relationships; the correlations are made with phenomena
outside the soil and portray conditions with whieh
the soils' characteristics correspond in certain details only.
OLIMATIO OLASSES
During the latter half of the last decade, the results or the Russian soil workers became known in
this country through the translation of Glinka's now
famous Die TYlJCn der Bodenbildung into German
and then English. The Russians contributed the
climatic point of view with regard to soil definition
and classification. Possessing a large country and
having observed that soil belts, like the blackerths,
corresponded in general to certain climatic belts
irrespective of underlying geologic formations, they
grouped soils in terms of the climatic forces presumed to have brought about the development of
their broad features. 1o .LtVthougll this interpretation
conforms much more closely to the facts than does
the geologic, as soils within a climatic belt possess
many important features in common, it refers, like
10 D. K. Glinka: The Great Soils Groups of the WOl'ld and Their
Devolopment, Mimeographed edition. Translated from the German
by C. F. Marbut, pp. 5-8.
8
MAJOR SOIL DIVISIONS
the geologic, to phenomena extraneous to the soil.
It suggests, by interpretation, what features the
soils may possess but it does not state them. Furthermore, field investigations have shown that climate does not account for a number of soil features
that are highly important.l l
:BOTANIO AND TOPOGRAPHIC OLASSES
The characteristic appearanco of given types
of vegetation on certain soils-forests on certain
light colored, and grasslands on certain dark colored soils-has long suggested the two-fold botanic
definition and divisions of "forest" and "grassland" soils and their secondary divisions of
"beach" soils, "bunch-grass" soils, etc. In like
manner, the occunence of given soils on given land
forms-flood plains, slopelands, uplands, etc.-has
given rise to groupings based upon such dish'ibution. In the case of both the botanic and topographic proposals, the qualifications refer to features incidental to the soil. Each of these factors
has a profound effect upon its characteristics, but
each indicates only indirectly, sometimes incorrectly, its true uttributes. Thus "upland" soils
within a few rods may be wholly unlike in fundamental features whereas many" grassland" soils
are as light colored as those with forest covers.
11 Marbut:
up. oit./
p. 5.
THE ATTRIBUTIVE SYSTEM
9
THE ATTRIBUTIVE SYSTEM
Without further examination of members of the
genetic system it is evident that all are open to like
objections. Each is based upon factors exterior to
the soils. None Teally expresses the soils' own features except by construction, and then only in so far
as the forces on which it is founded operate.
The only kind of classification appropriate for the
type of study here proposed must be attributive in
character-one in which the soils' own properties
form the basis of grouping. This basis is absolute,
not relative, for it describes the soils in exact terms.
It focuses attention upon the soil itself, moreover,
and not upon an external phenomenon.
As the properties possessed by soils are many in
number, it becomes a matter of comparison and
selection as to which of them possess the several
categorical requirements outlined on a previous
page, namely, those of fundamental character, those
in harmony with the other properties of the soils
of the group, and those of greatest universality.
CHROMATIO CLASSES
One of the more easily discerned properties of
soils is their coloration, and it has long been custom~
ary to designate and group soils in accordance with
this characteristic. The classification is of particu~
lar interest in view of the fact that it was given
official recognition and employed as the basis for the
highest category in the case of the well-known and
10
MAJOH SOIL DIVISIONS
widely copied" Soil Regions" map of C. F. Marbut
and associates of the Bureau of SOilS.12 The major
divisions are designated as "Light Colored Soils"
and "Dark Colored Soils" and the sub-groups
of each bear specific color names-brown, black, etc.
-but are also qualified in other respects.
One of tho principal drawbacks to a chromatic
grouping, in meeting the requirements of this study,
is the fact that the colors of normal soils are not
always in harmony with their other, sometimes more
fundamental, associate features, two soils of like
color being frequently dissimilar with reference to
other basic physical and chemical properties. The
light colored grayish and brownish soils of: the Great
Plains, for example, differ in very important respects from soils or similar colorations on the eastern Till Plains.
TEXT'UltAL CLASSES
The time-honored division of soils into light and
heavy textured groups, though founded upon true
soil properties, is, as in the case of the chromatic
scheme, a system in which the basic feature is not
infrequently out of harmony with its associate characteristics,13 for soils of like texture often differ
widely in other more important attributes. Thus,
outside o~ texture, the normal silt loams of North
Dakota are entirely difforent from those of Ohio.
Textural differencos are generally of much local
importance, but they arc subordinate features when
12
l8
Cf. Appleton's Modern Sehool Atlas, pp. 20-21.
Marbut: op. cit., p. 16.
THE ATTRIBUTIVE SYSTEM
11
viewed in a broad way, and accordingly cannot be
used for comprehensive regional studies except in
a secondary manner.
MATURATAL OLASSES
The Pedologic Cycle.-Probably the most significant ascertainment of modern soil science is the interpretation that soils pass through cycles of development resembling those of other changing natural
phenomena, that is, that there are young, mature
and old soils. This construction does not imply that
every soil will eventually pass through the complete
cycle from infancy to old age, but that when conditions favorable to the completion of the cycle do
exist in the case of any soil, such a soil, in the course
of time, becomes mature and then old. The real significance of this philosophy is the fact that it furnishes a key to both the striking differences between
certain soils which, on casual analysis, it would appear should have been alike, and the close resemblance between other soils, which, for analogous
reasons, should be dissimilar.
Mature Boils.-Mature soils have normany developed profiles. ("The series of layers in any given
soil is designated as its profile and its characteristics are made up of the sum total of the characteristics of the layers in its profile.") 14 They are characterized by those features which all soils of a given
environment acquire when comparatively undistur'bed by erosion or deposition through an extended
period of time. They occupy relatively level sur14
Ibid., p. 8.
12
MAJOR SOIL DIVISIONS
faces, such as smooth uplands and terraces, and are
formed under good drainage conditions. They are
free of abnormal characteristics resulting from the
presence in the parent material of large amounts or
certain constitutents, like sodium carbonate, which
produce clay hardpans and other unusual reatures.15
"Soils are designated as mature which have reached
a stage of development marked by the practical absence of geologic features and the great predominance of chamctel'lstics acquired during development. "10 They have "assumed the profile features
characteristic of the predominant soils on the smooth
uplands within the general climatic and botanic region" 17 in which they are found, and in theory have
adjusted themselves to all normal influences or their
environment.
Young Soils.-Young soils have incompletely developed profiles and show the characteristics or their
parent material to a greater or less degree.Is They
occupy flood plains, where they are periodically rejuvenated by the deposition of new sediments, or
hilly lands, where the surface is being continuously
removed by erosion and the underlying undeveloped
formations are brought to the surface. In both
cases the evolution of the soil is constantly retarded
or set back as the new materials repeat the changes
of youth.
Ibid., pp. 8-11.
Shantz and Mal'but: op. aU., p. 128.
17 C. F. Marhut and C. B. Manifold: The Soil of tho Amazon
Basin in Relation to Agricultural Possibilities, Geogr. Rev., Vol. XVI,
1926, p. 426.
18 Shantz and Marbut: op. c"t., p. 129.
16
16
THE ATTRIBUTIVE SYSTEM
13
Old Soils.-Old soils have passed maturity. They
have lost some of the essential characteristics of
normal soils and have acquired abnormal features,
like those of indurated hardpans.19 Most of them
occupy old flat land surfaces of earlier topographic
cycles where they have been undisturbed for long
periods of time.
The time required for a given soil to pass through
a complete cycle of development is not known, the
period exceeding man's short life span many times.
It varies widely with both soil material and environment, moreover. Soils are therefore essentially
"permanent n as far as man is concerned. The
changes brought about in their features in the
course of his life are from his standpoint entirely
negligible.20 Yet each age group has a distinctive
bearing upon man's activities.
This relationship (young, mature and old) has
also been proposed as a basis for establishing major
soil groups. But soils developed under different
environmental conditions are markedly dissimilar
(pages 34 ff.). Not only the mature and old but also
to a great extent the immature soils of one region
are quite unlike the corresponding age groups of
another. Immature soils, moreover, similar to the
immature members of the animal and plant lcing~
dom, do not form a group coordinate with the mature and old members.
19
:;10
Ibid., p. 128.
Marbut: op. cU., p. 13.
14
MAJOR SOIL DIVISIONS
OTHER PHYSICAL CLASSES
Classifications mayor have been based on a num~
ber of other physical characteristics, snch as drainage conditions (well drained and poorly drained)
structure, consistence, etc., but each of these also
lacks in some way the necessary qualifications. R~­
course will therefore be made to chemical features,
which, like the physical, offer a variety of possibilities.
CBEMICJAL CLASSES
Lime-Accumulating and Non-time-Accumulating
Soils.-The most striking and unique scheme of classification based upon the soils' chemical features is
that proposed by Marbut who, restricting his groups
to normal mature members, separates the soils of
the United States into two major divisions, which
he qualifies as lime-accumulating and non-lime-accumulating. The lime-accumulating soils are "characterized by the presence on some horizon [usually
the 'suDsoil'] of the solum [a term used by pedologists to indicate the soil exclusive of its underlying
parent material] of a layer of lime carbonate . . .
present in higher percentage than in the parent
material" and curiously developed regardless of the
nature of the accumulation from which the soils
evolved. The mature soils of the associate division
"do llot have such a horizon even in those cases
where the soil has been developed from parent materials rich ill lime carbonate," and in positive characteristics are distinguished "by the presence of a
THE ATTRIBUTIVE SYSTEM
15
zone in which sesquioxides [most markeilly those
of iron and alumina] have been shifted from one
position and [noteworthily] accumulated in another
in the soil profile during the progress of soil profile
development." 21
Geographic Attributes.-Although devised primarily as the basic scheme of classification for pedological studies, this method of grouping the soils
not only meets the categorical requirements laid
down on an earlier page for this geographic inquiry
but it also includes several features of particular
merit. To begin with, it is limited to mature soils,
the age group most representative of what might be
designated the normal geographic conditions of a
region when viewed in a general way. Having adjusted themselves to the normal features of their
environment, mature soils most completely reflect
its peculiarities throughout its area of distribution.
They have regional qualifications. Like the type
study, they symbolize the normal soil conditions of
a given area.
In the second place, this plan of division separates
the soils into two groups of very unlike fundamental
character. When regal'ded as a whole, the associate
basic features of each division, aside from the condition of calcium carbonate accumulation, are divergent and contrastive as regards not only physical
but also chemical attributes. And of more immediate interest, such differences are necessarily productive of corresponding contrast in geographic
relationships.
21
Ibid" p. 18.
16
MAJOR SOIL DIVISIONS
Another important attribute of these divisions is
tho character of their distribution. Each is easily
expressed graphically. The non-lime-accumulating
soils occur chiefly east of a 'line extending approximately from the northwestern corner of Minnesota
southward to the vicinity of Corpus Christi, rrexas. 22
The lime-accumulating soils lic west of this line.
The latter division does not occupy tho western part
of the United States exclusively, as local bodies of
the non-lime-accumulating soils are scattered
throughout this region, especially west of the Great
Plains.
Nomenclature.-Several names have bccn proposed for these major divisions. For intcmational
use, Shaw has offered the Latin names Sinecalcis
(without lime) and Cumcalcis (with lime}.23 Marbut has suggested the tel'ms Pedalfers (soil~ with
aluminum and iron accumulations) for the non-limeaccumulating soils, and Pedocals (~ons with culchnn
carbonate accumUlations) lor the lime-accumulating
division. 24 Neither of the proposed names has been
officially accepted, but pedalfer and pedocal arc used
in this study. They are based upon the same root
as the widely used name or the science, pedology,
and indicate the chu,racteristics of the soils in positive terms.
The Problem of Variation.-Like all major divisions, these groups embrace variations or subgroups
221boid., p. 19.
23 C. F. Shaw: A Uniform Intcl'llational System of Soil NomenclatUre, Proc. and Papol's First lIlt'1. Congo Soil Sci., Com. V, 1927,
p. :16.
24 Marbut: op. cit., p. 20.
THE ATTRIBUTIVE SYSTEM
17
of diverse character, namely, color, structure, chemical composition, etc. Although it is impossible, in a
study of limited scope, to give extended consideration to such diversity, it is recognized that differences within major groups are important and are
deserving of attention. Such differences may be
pointed out in a general way without very specific
reference or they may be associated with concrete
known phenomena. It is obvious that the latter is
the more enlightening method. Accordingly, the
essential features of larger secondary groups into
which the major divisions may be resolved are summarized in the succeeding pages of this chapter beIore the characteristics and relationships 01 the
great divisions are further presented. In subsequent chapters, then, where variations in the major
divisions arise, the reader may be referred specifically to the subgroups for the condition or qualification under consideration.
Although each of the divisions may be divided into
a series of descending categories, the lowest of
which includcs soils differing in only a single respect, it best serves the purposes just outlined to
consider only that subdivision to which the term,
great soil groups, is applied by pedologists. Though
designated chiefly by chromatic names and corre·
sponding in a general way with the distribution of
certain climate types, it is emphasized that the
groups are not delimited on the basis of either, but
are defined solely on the basis of their own peculiar
profile features, briefly outlined below. A scientific
nomenclature for these groups has not yet been
18
MAJOR SOIL DIVISIONS
worked out and the names employed are used primarily for identification only. The descriptions aim
to bring out, moreover, only such features of the
soils as are essential to their understanding as used
in this study.
THE GREAT SOIL GROUPS
TIlE PEDALFERIO GROUPS
The pedalfers are made up of five great subgroups to which the names pod sols, gray-brownerths, red-and-yellowerths, ferruginous laterites and
prairyerths have been applied. 25 Podsol, a folk term
applied to the gray soils of northern Russia, has
been adopted in the American literature to designate the soils of similar character in the northern
part of the United States. Gray-brownerths, rcdand-yellowerths and prairyerths have been proposed by the author in place of the long, cumbersome phrases soil workers have commonly employed
for the grayish brown forest soils, the red and yellow forest soils, and the prairie soils of the United
States. In the absence of a thoroughly scientific
nomenclature, the names are more compact and aim
to preserve the qualifications by means of which
these soils are known. Laterite is the term universally applied by pedologists to certain red soils of
the tropics, the name having been derived from the
Latin word ~ater) a brick. (In India the material
2~L. A. Wolfangor: Major World Soil Groups and Somo of Their
Geographic Implications, Geogr. Rev., Vol. XIX, 1929, p. 102.
THE GREAT SOIL GROUPS
19
is extonsively cut up into blocks and used in build.
ing.)
The podsols, gray-hrownerths, rcd-and-yellowcrths and the ferruginoul:l laterites form a series of
east-west belts succeeding from north to south, in
the order given, in thc cast ern part of the major
pedalferic zone i the prairyerths compose a llorthsouth belt adjacent to the western boundary.26
(Refer to the map.) Outliers of all groups, except
the ferruginous laterites, also outline lessor bodies
west of the Great Plains, where, owing to rapidly
changing conditions over relatively small areas, the
regularity of occurrence i8 broken. Only the larger
of these are indicatGd on the map.
Although the area of distribution of these groups
includes soils in all stages of development, the unqualified references made to the groups apply only
to the mature members, for these alone, as previously
explained, possess the distinguishing group characteristics in their entirety. These members are not
only the bases for the groups' definitions but they
are also most representative of the normal soil conditions of their respective rebl'jons. It is impossible,
on account of the scale employed, to show the distribution of the soils that have reached this stage
of development, as they ure so intimately intermixed
with soils of other ages; thus the map shows only
the region of their occurrence. In accordance with
their definition, they may in general be visualized
as mantling most well-drained smooth areas. This
statement is not to be interpreted to mean that all
~
Marbut: op aU., pp. 21-22.
20
MAJOR SOIL DIVISIONR
such areas have normal mature soils. It is merely
an indication that the soils of such areas are likely
to be mature. Thus the Till Plallls of the Central
Lowland Province ar~ by no moans a region of mature soils only, although the proportion OL the members of this age occurring here is large.
The Podsols.-The largest body of podsols in
North America lies in southern Cnnada but the
group is represented by several large areas in the
humid northern part of the United States. The soils
are extensively developed in the Upper Lakes Region, the Adirondacks and northorn Now England,
with outliers of small dimension mantling parts of
the Appalachian Platlmu, extending from western
New York to West Virginia,27 and local areas in the
mountains and high plateaus of tho West. They
comprise the relntively higher latitude and high altitude soils of the United States.
The characteristic profile features of the podsols
under virgin conditions are: (1) the surface layer
of raw humus or brown vegetable matter, consisting
of leaves, sticks and moss, ranging up to It foot in
thickness; (2) the acid, gray to nearly white upper
mineral horizon which, in the fully developed soil,
is highly leached, free of decomposition products,
and lighter textured than the subsoil; and (3) the
dark brown or coffee-brown subsoil or lower horizon
which "has a relatively high cont{mt of organic matter, iron and alumina." 28 The percentage of soluble
:<17 U. S. Dept. Agr., Field OpOl'atiollB, Bureau of: SOilA, 1022, p. 906.
C. F. Marbut: The Contribution of Soil Surveys to Soil Science,
Soc. :for Prom. Agrl. Sei., Froe. of Forty·First Anll. Meeting, p. 134.
28
THE GREAT SOIL GROUPS
21
plant foods is very low, although the alkalies and
alkaline earths locked up in the undecomposed minerals of the soil mass may be present in abundance.
The structure of the A horizons 20 (as the surface
layers are usually clesignah\d) of the heavy textured
soils is simple, single grained or slightly platy,
whereas that of the B horizons (the "subsoil") is
compound, the soil mass "breaking into angular
fragments when dry. "SO In both chemical and physical characteristics the podsols are poor soils.
The Gray-Brownerths. - The gl'ay-brownerths
occur in both the oastcrn and western parts of the
United States. They lie between the podsols forming the northern marginal belt of soils in the eastern
part of the United States, and the red-ancI-yellowerths of the southeastern part. They also form a
broken north-south belt in the PacifiC states where
their continuity is interrupted chiefly by extensive
bodies of rough broken land. Local areas of relatively small size are also scattered through the
Rocky Mountain System and the highlands of the
Intermontane Plateau but most of these do not
appear on the map, as the rough broken land obscures their identity. These soils constitute the only
major group extensively developed in both halves of
the country.
The more striking group features of these soils
are their brownish coloration, mild acidity, well de. ~o Report of Committeec'{)n Terminology, Soil Torminology, Amer.
Soil Survey .Assn., Bull. IX, p. 36.
&0 M. Baldwin: Some Chal'!Hlteristic Profiles in tho North Central
States, Amer. Soil Survoy .Assn., Bull. VII, Vol. I, p. 124.
22
MAJOR SOIL DIVISIONS
veloped nut-like structure, and the moderate extent
to which they are leached. I...Jilm all pedalfers, they
are non-lime-accumulating and have 13 horizons relatively high in iron and alumina. Unlike the podsols,
however, organic matter docs not accumulate in the
subsoil.
Although most of ihe soils are basically brown,
the color is seldom unmixed, and shades, tints or
combinations with red, yellow and gray are common.
A generalized description of the group in eastern
United States may be taken as repreHelltative of the
co lor profile. The soils arc forest soils, ilw dominant natural vegetation consisting of associations
of deciduous trees, such as maple, birch, beech, oak
and yellow poplar. Hence, "where undisturbt>d, the
surface has a covering of loaf' litter . . . 1. to 3
inches thick, underlain by a very thin layer of nearly
black leaf mold. The upper mineral soil horizon
(A) is dark grayish-brown in the upper portion
where organic matter is relatively abundant, grayish-brown or grayish-yellow below. . . . The second
major horizon (B) is brown or yellow-brown in
color." 31 The more southerly soils usually have
reddish tinted horizons, and darker and lighter
gradations of all colors occur everywhere. The C
horizons, as in all soil groups, are variable, owing
to the diverse nature of their formation.
The precipitation uuder which these soils
evolved, about 30 to 45 inches annually, has leached
the carbonates from tho solUlu, but the soils aro only
81 M. Baldwin: Tho Gray·Brown Podsolie Soils of Eastorll United.
States, Proe, and Papers First Int'l. Congo Soil SCi., 1927, p. 277.
THE GREAT SOIL GROUPS
23
mildly acid, and their lime requirements as a group
are relatively low. With the exception of the prairyerths, they are less acid than any of the pedalfers.
Within a soil itself, acidity normally increases with
depth, although in those derived from calcareous
material the reaction naturally changes in the C
horizon.
Excluding the prairyerths, the gray-brownerths
are also the least leached of the pedalferic division.
Their content of organic matter, alkalies and alkaline earths is low, but it is not as low as that of the
other groups, the difference being appreciable and
significant. Although the larger part of the soluble
materials formed are removed in solution during the
process of its evolution, the proportion present in
most of the soils is larger than that of the other
groups.S2
The well-developed structure of the soils is one of
their chief assets. It is not vcry well marked in the
A horizons, which are usually composed of single
grains only. The B horizons have a very prominent
structure, "the mass breaking readily into angular
lumps, ranging in diameter from liz to 1 inch, increasing in size downward." sa Although subject,
under cultivation, to rather rapid deterioration in
common with the other light colored pedaliers, the
structure of the gray-brownerths is relatively more
durable, as the lower acidity apparently makes the
structural aggregates more resistant.
32
8a
Marbut: op. ait., p. 134.
Baldwin: op. aU., p. 277.
24
MAJOR SOIL DIVISIONS
The Red-and-YeUowerths.-The prevailing colors
of the mature soils of this group are red or yellow.
Because the general characteristics of these soils,
with the exception of color, are quite similar, they
have not been separated on the map. The yellowerths are developed chiefly on the South Atlantic
and Gulf Coastal Plains and the southern part of
the Appalachian Plateau. The typical Piedmont
soils and those of the Tennessee section of the Valley and Ridge Province are redel'ths. Reddish yellow soils representing the transition between yellowel'ths and rederths occur in the Mississippi upland
loess region and on the more rolling arcas of the
Coastal Plains.
Although basically in variance with the graybl'ownerths, the soils of this group, taken as a whole,
are in some respects like the more northerly soils.
"The dark colored surface layer in the natural
forest-covered soil is usually somewhat thinner and
grayer" and the lower surface horizon is "yellow,
often pale yellow, rather than yellowish brown."
Though having similar A horizons, the B horizons
of the rederths are red and of the yellowerths yellow. "In both cases there is a wider difference between the textures of tho A horizon and the B horizon than is the case in the" gray-brownerths. "The
true soil layer, including the A and B horizons, is
thicker. . . and the percentages of lime, magnesia,
potash, and soda are in general lower" than in the
gray-brownerths.S4
84 u. S. Dept. Agr., Field Oporations, Bureau of SoilS, 1921,
p. xix.
THE GREAT SOIL GROUPS
25
The sandy Coastal Plains soils are essentially without structure but, owing to their light texture, they
are friable. 'fhe heavier textured rederths and yellowerths have a moderately coarse, angular, nut-like
structure similar in a general way to that of other
humid soils of the Unitod States. Tl18 structure
under cultivation is more subject to deterioration
than that of the gray-brownel'ths, as the lime content is lower and the colloids are more susceptible
to deflocculatioll.
Owing to the fact that the red-and-yellowerths are
somewhat more thoroughly leached, their minerals
more completely decomposed,sll and their structural
characteristics inferior to those of the gray-brownerths, they are poorer soils in thoir natural condition. The open winters under which they have developed have exposed them to continuous leaching.
The sandy textured yellowerths of the Coastal
Plains are as a whole somewhat poorer than the
heavier textured soils of the red-and-yellowerth region, because the coarse materials have been more
favorable to the leaching processes.
The Ferruginous Laterites.-The region occupied
by this group is the least extensive of all the great
soil groups. The proportion of the area occupied
by the typical normal members is relatively the
smallest also, the principal development being confined to southern Georgia.
The general features of the profile are substantially similar to those of the yellowerths of the
Coastal Plains, but the soils are characterized by the
85
Marbut: op. cit., p. 134:.
26
MAJOR SOIL DIVISIONS
"occurrence of indurated bodies of impure iron
oxide occurring in the form of pebbles, seams,
ledges, and surface coatings or crusts." no The
small rounded brown aggregates arc particularly
conspicuous, and the land is populady referred to
locally as "red pebble" or "pimple" land. The
soils lie at the outer margin of the great tropical
zone in which the lateritic process of soil development 81 operates most vigorously. The mature soils
associated with them, particularly in Florida, appear to llave been derived from materials low in
iron, and the prevailing soils of this state are without such accumulations. The ferruginous laterites
are moderately to strongly acid and "quite thoroughly leached of soluble materiaL" 88 They are
not unproductive, however, but are regarded as
"strong" desirable soils in the areas in whieh surveys have been carried on.311
The Prairyerths.-Although included with the
pedalfers, the distinguishing features of the prairyerths are not in harmony with those of the other
great groups of this major soil division. The chief
point of resemblance is the ,fact that the soils are
non-lime·accumlllating.
The soils, in contrast to their light colored forest
associates, developed under grass covers and ac80 E. D. Fowlor: Iron ACCUIDuhltion in Soils of tho Coaatal Plain
of tho Southeastern United States, Proe. and Papers First Int'l.
Oong. Soil Sei., 1927, Com. V, p. 436.
3? H. Hal'l'assowitz: Laterit, Berlin, Gebriider Borntrager, 1926.
8B Fowler: op. cit.
80 U. S. Dept. Agr., Field Operations, Bureau of SOils, 1918, p.
501; 1920, p. 1644; 1923, p. 285.
THE GREAT SOIL GROUPS
27
quired dark colored A horizons rieh in organic matd
ter. The B horizons are brownish or yellowish but,
unlike the typical pedalfers, they are not markedly
heavier textured than the surface layers. They are
likewise but slightly leached and are comparatively
well supplied with soluble salts. They have a pronounced granular structure. The soils are low in
lime but not essentially acid. 40 As a whole, the
prairyerths comprise one of the better great soil
groups of the United States.
Special attention is directed to the southern members of this group, the black prairie lands of Texas,
owing to the general similarity of some of their features to the typical normal prairyerths. They are
immature soils. The black waxy lands are Rendzinas, owing their dark color and high friability to
the presence of an unusually large amount of lime
inherited from the parent material, whereas the wet
prairies of the Coastal Plains represent a drainage
condition.41
THE l'EDOCALIO GROUPS
Only four great subgroups may be distinguished
among the pedocals: the blackerths, the chestnuterths, the brownerths, and the grayerths.4,~ The
principal bodies form a series of succeeding northsouth belts beginning with the blackerths in the east
40 T. D. Riee:
Profile Studies of Representative Soils in the
Northern Prairie States, Amer. Soil Survey Assn., Bull. vn, Vol. I,
pp. 1-5, 11-14.
41 U. S. Dept . .Agr., Field Operations, Bureau of Soils, 1915, p.
1071; 1920, pp. 821, 380-383.
42 Wolfanger: op. cit.
28
MAJOR SOIL DIVISIONS
and progressing westward in the order named. 4s
Throughout the Western Highlands their continuity
is frequently interrupted by rough broken land and
numerous local bodies of the pedalferic groups.
The names of these groups have been proposed by
the author on the basis of the same principles as
those of the pedaHeric division. The blaekerths are
the chernozems (the Russian term for blackerths)
of pedologic literature; the chestnutel'ths, the chestnut colored soils; the brownerths, the arid brown
soils; and the grayerths, the gray desert soils. As
in the case of the pedalferic soil groups, the descriptions and relationships allude only to the matm'c
members.
The Blackerths.-The blackel'ths, forming the
most easterly belt of pedocals, lie adjacent to the
prairyerths. These two great groups have many important features in common. Both have dark colored .A horizons, yellowish or brownish (typieal1y
reddish toward the south) B horizons, and well-developed granular structures. Both are relatively
non-acid, unleached, and have ample stores of organic matter and mineral plant foods. Differences
with regard to the properties mentioned exist, but
they are secondary differences. In fact, in field investigations carried on by the author and others in
the two chief regions in which these groups occur,
the soils of both groups were for a long time not
recognized as possessing significant differences. It
is now known, however, that the blackerths are
43
c.
23-25.
F. Marbut: A Scheme :fo~ Boil Clnssification, ap. oit., pp.
THE GREAT SOIL GROUPS
29
darker, have a more perfect granulation, possess a
higher content of soluble mineral matter, and are
almost neutral or alkaline in reaction. As far as
general soil characteristics are concerned, they are
the more desirable of the two groups. They have
all the features which" good" soils should have.
The chief distinguishing dissimilarity in the
groups is the zone of calcium carbonate accumulation of the blackerths and the absence of such an
accumulation in the prairyerths. The blackerths,
like all pedocals, "have been developed under conditions of a moisture supply insufficient to maintain
a continuous downward movement of moisture to
an indefinite depth" 4~ and carbonates formed in decomposition, or occurring in the parent formations
and dissolved by percolating waters, have been deposited in the lower part of the zone of penetration.
Other more soluble compounds are also deposited,
but in periods of exceptionally heavy rainfall they
are redissolved and removed. The total loss of soluble material is relatively small and insignificant,
however, when compared to that of the prairyerths
where the average rainfall is adequate to sustain a
predominant moist condition to considerable depths.
The Chestnuterths. - Typical chestnut colored
soils form only the central part of this belt, the
shades of the surface horizons varying from dark
brown in the north to dark reddish brown in the
south, whereas those of the subsoils range from
4~ C. F. Marbut: Report of Subcommittee on the General Soil
Map of the Americas, Proc. and Papers First Int'I. Congo Boil Sci"
Proceedings, p. 263.
30
MAJOR SOIL DIVISIONS
brown to reddish brown. In any given latitude the
colors are typically lighter than soils of the adjacent
blackerths/ 5 owing to the westward decrease of precipitation and density of the vegetative covering.
Although the content of organic matter is lower, it
is quite adequate for crop production,
As the depth of penetration of percolating waters
is less than in the blackerth region, the zone of lime
accumulation is shallower, and the upper horizons
have not been leached of their soluble mineral plantfood elements to any appreciable depth. The structure, nevertheless, is imperfect. The ideal granulation of the blackerths is not developed, the soil
masses being columnar or cloddy. Under cultivation the soils produce good seedbeds, however, as
the aggregates break down and form a good tilth.
The Brownerths.-" The soils of this belt are the
lightest in color of all the Great Plains soils and
the carbonate zone beneath them is shallowest. The
color of the soil is brown rather than distinctly dark
brown, but, as compared with the lighter colored
soils of the deserts, it may be placed, with sufficient
justification, with the dark colored soils. Like the
other Great Plains soils it has developed under a
grass cover but one of somewhat less dense growth
than those on the other belts. These soils, where the
belt in which they occur is not bounded on its wcst~
ern side by the mountains or by the 'Mountain foot'
belt of darker colored soils, change westward by
imperceptible gradations into the still lighter col~
ored soils of the aeserts." <16
45
46
C. F. Marbut: Soils of the Great Plains, op. cit., p. 58.
Ibid" p. 64.
ROUGH BROKEN LAND
31
The structural features of the brownerths have
not been worked out. If the soils as observed in
Colorado may be taken as representative, the A
horizons are structureless or loosely defiocculated
and the B horizons show columnar breakage. 47 The
low rainfall under which the soils occur indicates
that they are wholly unleached, that is, few or no
soluble materials have been removed from them.
The Grayerths.-The grayerths vary from light
brownish gray in the north to reddish tinted soils
in the southern part of the region. The typical surface horizon is a thin "desert crust" or a thin pebbly layer which forms the so-called "desert pavement." Its substructure, the" desert mulch," is a
light, porous material of little compaction. The
upper subsoil is also porous but it is compact and
brown in color. It is underlain by the zone of lime
accumulation, which under the low rainfall conditions of the desert is shallow and which in the older
soils frequently forms a firmly cemented hardpan.
Leaching, moreover, has been reduced to a minimum but the soils are necessarily low in their eon~
tent or organic matter.48
In the description drawn for the several pedocalic
great soil groups, it will be noted that reference has
been made to certain differences between the soils
occupying the northern and southern, or the central,
northern and southern parts of the belts. Thus, the
Dakota. blackerths are the blackest or the sub-humid
group; the Nebl'aska~Kansas division is very dark
47
Ib'a,., p. 65.
M. H. Latham: Some Profiles of Representative Western. SOils,
Amer. Soil Survey Assn., Bull. VII, Vol. I, Pll. 23-4a.
48
32
MAJOR SOIL DIVISIONS
brown; and the North Texas-Oklahoma division is
dark brown. The South Texas division is also
dark brown, but its zone of lime accumulation is
characteristically indurated, forming the so-called
"caliche," and this zone attains a thickness IDucl1
greater than that prevailing in the more northern
blackerths. The blackerths, therefore, are not w}1011y
black soils. They are merely the darkest bolt of
pedocalic soils and possess the deepest zone of limo
accumulation. Corresponding differences from north
to south may also be observed in the chestnuterths,
brownerths and grayerths, the former including the
darkest, and the latter the lightest of the pedocals
aside from those of the blackerth group.
Expressed graphically, the darkest divisions of
each group form a general east-west belt along the
northern part of the pedocalic zone, the less dark
divisions an east-west belt south of the first, and the
lighter divisions similar belts in the southwestern
part of the United States. In reality, then, the
pedocalic region, unlike the pedalferic, presents, as
explained on a subsequent page (65), a rough gridiron pattern of secondary soil groups. With the
chief exception of several reconnaissance studies
and the county surveys centering principally upon
western Nebraska, however, but little precise information is available on the divisions of the three
Ughter colored great soil groups and their features
of much significance to this study are not well understood. On the other hand, certain differences in
the use of a given north-south belt correspond with
the distribution of the secondary soil divisions (see
ROUGn BROKEN LAND
33
page 113). Albeit it is known that such differences
may be correlated with climate, it is very probable
that a more detailed study of the soil factor will
also bring out the nature and importance of the
edaphic relationships.
ROUGE: BROKEN LAND
This group, confined largely to the Western Hig1ilands, includes chiefly the larger areas of steep,
rocky and broken land. It embraces numerous bodies of mature soils belonging to the great groups
developed in accordance with the laws of the vertical
distribution of soils,49 but the areas are too small to
be indicated on the map.
4U V. Kokutschajeff:
On the Theory of the Zone in Nature, The
Horizontal and Vertical Zones, 1899 (RUBsian), Quoted by Glinka,
o1J. ait., p. 44.
CHAPTER II
THE PEDALFERS
The soils of the United States are unequally dis~
tributed, as regards area, between the major soil
divisions. As the pedalfers occupy the entire eastern half of the country as well as numerous areas
scattered through the West, their proportionate extent is somewhat larger. The western mountains,
moreover, include much rough stony land on which
soil development to any appreciable extent has taken
place only locally.
An analysis of the evolution of any object serves
to throw its characteristics into greater relief. The
factors involved in the development of the soils and
their general effects upon soil evolution will be
briefly summarized, therefore, before the soils properties are more fully described and their geographic
relationships reviewed.
The active environmental conditions under which
the major soil divisions have evolved are markedly
unlike in character. The pedocals are the product
of a low average annual precipitation and a natural
vegetation consisting of grasses or shrubs; the pre~
cipitation under which the pedalfers have developed
averages from 25 to more than 60 inches annually,
34
35
THE PEDALFERlC ENVIRONMENT
and the typical natural vegetation is forest. These
contrasts, low versus high precipitation, and grasses
versus forests, are not only the most antithetical
but also the most powerful influences to which soils
are subject. They bring about the significant, fundamental differences between the major soil divisions. The passive environments, on the other hand,
are more or less similar. The topography and parent material from which the soils of both divisions
evolved are essentially alike. They have produced
diversities within rather than dissimilarities between the major divisions.
THE PEDALFERIO ENVIRONMENT
OLIMATE
Of the active environmental elements, climate is
the most potent in determining a soil's (mature)
basic characteristics.1 In fact, one of the cardinal
principles of modern soil science is the doctrine that
"climatic forces are the predominating soil-forming
agencies of the world." III Under their powerful influences, soils evolving from unlike materials acquire
fundamental features in common. They control the
moisture and temperature conditions under which
the complex changes in both mineral and organia
matter take place, superseding the effect of all other
fu~rn!
2
Glinka: op. cit., pp. 5-8.
Shantz and Marbut: 01'. cit., p. 120.
B
GliDka: op. oit.
1
.
36
THE PEDALFERS
Precipitation.-The pedalfers are "humid" soils.
They have developed under humjd climates. The
minimum average annual rainfall under which they
occur is about 25 to 30 inches, tho amount necessary
to produce their features varying slightly with such
factors as latitude and parent materials. Northorly
situations with less precipitation and lower evaporation are obviously comparable to morc southerly
areas with greater precipitation but higher evaporation. Under given climatic conditions, moreover,
the soils derived from coarser parent materials absorb moisture more rapidly and hence experience
the effect of morc "humid" conditions than soils
evolved from finer consiitutonts. Whatever the variatlOn, the effect of tho com11inod factors must bo
such as "to maintain a permanent moist condition
of the soil and parent material down to the permanent watertable."4 When this circumstance obtains,
the resultant soils formed arc pedalferic.
Provided that the precipitation is adequate to
maintain the conditions jnst outlined, its distribu.
tion and character are of no consequence in the de~
velopment 01 pedalferic soils as such. In the Pacific
region the maximum precipitation occurs in the
winter season and the summers are moderately dry,
but the soils are similar to those 01 the humid ('aRtern part of the United States 3 whore the precipita-
"c. F. Marbut: Outline of a Sehllme for tho Differontiatioo of
Soils into Mapping Units on It Uniform Basis for all Countries,
Froe. and Papers First Int'I. Congo Soil Sei., Proceedings, Gencrnl
and. Special
S(l~8ionsJ
p. 263.
U. S. Dept. Agr., Field Oporations, Bureau of Soils, 1917, :po
2434i 1919J pp. 1846-1847.
5
THE PEDALFERIC ENVIRONMENT
37
tion has a summer emphasis. Nor docs the fact
that the winter precipitation comes in the form of
snow in some parts of the area of distribution of
these soils affect their fundamental features as
pedalfers. The diversity in temperature, which the
differences in the character of the precipitation
imply, merely gives rise to diversification within
the division.
Temperature. - The average monthly temperatures under which the pedalfers of the United States
have developed range from less than 0° F. to more
than 65° F. in January and from less than 65° F.
to more than 80° F. in July.16 As just indicated, the
differences in temperature are signiilcant in bringing about tlie development of unlike groups within
the pedalfers. At one extreme are the podsols,
evolved under climates having long cold winters and
short summers; 7 at the other extreme lie the ferruginous laterites of the southeastern Coastal
Plains, where temperatures rarely fall below freezing.a The position of the red-and-yellowerths, the
prairyerths, and the gray-brownerths places them in
an intermediate situation. The prevailing climate
of the red-and-yellowerths is that of the so-called
Cotton Belt and that of the prairyerths is the western part of the Corn Belt. The eastern gray-brownerths are in the climatic environment of the upper
Ohio Valley and the Middle Atlantic states, whereas
Ward, op. cit., pp. 82-87.
M. Baldwin: Some Characteristic Profiles in the North Central
States, ap. oit., p. 123.
8 Fowler: op. cit., p. 435.
Q
7
38
THE PEDALFERS
the Pacific group has the typical marine mild-wintermild-summer type 0 of the West Coast. The exact
climatic conditions of any part may be readily ascertained by comparing the accompanying soil map
with appropriate climatic maps.
NATlmAL VEGETATION
Secondary to climate but of major significance in
its influence upon the fundamenul features of soils
is the effect of the natural vegetation.lO Determined
in a broad way by climate, it "plays an important
part both as a living organism and as a dead organic
substance l ' Xl the relationships of which will be presently noted.
TKe prevailing natural vegetation of the pedalfers, exclusive of the dark colored prairyerths, was
forest. (The prairyerths, because of their exceptional features, will be considered separately, and
all generalizations made throughout this study with
reference to the pedalfers as a whole does not include these soils unless specifically qualified.) Outside of poorly drained and other areas affected by
local conditions, the stand appears in general to
have been continuous. It was not savannah or park~
land, as is so characteristic of great regions in the
tropics. The surface of the ground was accordingly
9 W. D, Jones and D, S, Whittlesey: An Introduction to Economic
GllogrnpllY, Vol. I, pp. 145-146.
10 Shantz and Marbut: op, cit" pp. 119, 129.
11 S. S, Neustruev: Genesis of Soils, Russian Podological Inves·
tigations III, p, 23.
THE PEDALFERIC ENVIRONMENT
39
shaded and was covered with an accumulation of
leaves, twigs and other arboreal debris.
Both great divisions of the forest formations of
the middle latitudes-coniferous and deciduousare represented in the pedalferic flora of the United
States.J.2 The dominant formation of the podsola
in North America and other continents is the Northern Coniferous Forest, but the northern hardwoods,
such as hard maple, beech and birch, afe also common.13 The broad-leaved hardwood associations
(birch-beech-maplc-hemlock, chestnut-oak-chestnut
-yellow-poplar, and oak-hickory) may be largely
identified with the gray-brownerths. The typical
forest associations of the rcd-and-yellowerths are
the southeastern pine forest and the oak-pine association, with lesser areas of the oak-hickory group
on the northwestern and western margins. The
southeastern pine forest is also characteristic of the
ferruginous laterites. The prevailing groups of the
western pedalfers are the western yellow pineDouglas fir and the cedar-hemlock associations of the
Rocky Mountain and Pacific Mountain systems.1'
P A.:RIlNT MATERIALS
The materials from which the pedalfers have
evolved embrace accumulations derived from repre~
sentatives of all the great rock groups, namely, sediShantz and Zan: op. cit.
J. O. Veatch: Profiles of Soils in the Great Lakes Region of
the United States, Proe. and Papers Firat Int'l. Congo Soil Sci.,
Com. V, p. 350.
1'Shantz and Zon: op. cit" pp, 11-14.
12
:LS
40
THE PEDALFERS
mentary, igneous, and metamorphic 1'ock8.15 Viewed
chronologically, moreover, the time groups involved
range from relatively recent unconsolidated deposits
to old crystalline pre-Cambrian formations. 1G On
the other hand, "in a study of the soils of a region,
taking into consideration their broad, genetic characteristics only, the influence of the parent material
may be mainly neglected or entirely so." 17 The striking relationship, therefore, is not the extent of the
formations included but the fact that such a variety
of originally unlike materials has given rise to 80
many soils with certain broad fundamental featurcR
in common. Irrespective of original derivation or
past geologic history, such soils as have reached
maturity in the pedalferic environment are ironand-alumina-accumulating but non-lime-accumulating, although derived in a numbor of cases from
formations carrying calcium-bearing minerals.
A similar discordance also characterizes the
relationship of the mature soils to their parent materials in the case of tho great soil groups. Tho graybrownerths, for example, are derived from such variable materials as loess, glacial accumulations, lake
deposits, marine sands and clays, and residual accumulations derived from limestones, crystalline
rocks, sandstones and shale.18 Yet the fully devel~
oped normal soils evolved from all these materials
15
U. S. Dept. Agr., Field Operations, Bureau of Soils, 1914:, p.
569 i 1911, p. 212; 1921, p. 1647.
~e Ibiil., 1914, II, 245; 1918, pp. 1144-1145.
11
18
Shantz and Marbut: ap. cit., pp. 120-121.
U. S. Dept. Agr., Field Operations, Bureau of Soils, 1917, pp.
819, 320, 379-380, 1150, 169G-1697.
THE PEDALFERIC ENVIRONMENT
41
are sUDstantially alike. Only when the less comprehensive groupings, such as the soil series, are taken
into account, can the parent geologic formation be
regarded as contributing noteworthy, albeit minor,
features 19 to the soils, but, as these lesser groups
are not within the scope of this study, the parentalgeologic relationships may be disregarded.
LAND FORMS
All major types of land forms-plains, plateaus,
hill country and mountains-are represented in the
peclalferic environment. The plains and plateaus
are of chief interest in this study, however, because
normal mature soils develop only on smooth, wel1drained surfaces/o and this type is the prevailing
configuration in such land forms. Although mature
soils are most characteristic of such land forms, they
do not occupy them to the exclusion of other age
groups. Details, such as flat and depressed, poorly
drained areas, or slopelands within the major type,
bring about much variation, even in such extensive
level regions as the Coastal Plains or the Till Plains.
Furthermore, mature soils develop also on smooth,
well-drained uplands within hill and mountain
country.
Questions frequently arise as to the proportion of
the total area of any soil group occupied by mature
members. No information is available on which any
satisfactory estimate may be based, because soil
mapping is yet too limited, and the percentage of
10
2Q
Ibid., 1918, p, 3.
Bhant:z; and Mal'but: op.
~t.,
p. 128.
42
TIlE PEDALFERS
smooth, well-drained land on which normal mature
soil development may conceivably take place is un~
known. Such facts are available only in the case 0'[
those areas, usually counties, in which detailed soil
surveys have been carried on. The difficulty in making even rough estimates for the great soil groups
as a whole based upon these surveys is illustrated
by Table I, which shows the percentage of mature
soils in two counties selected from the area occupied
by each great soil group. The figures given arc
approximate, since the interpretation of certain less
extensive soil series as fully developed normal mature soils is open to several conclusions. They cannot be accepted, moreover, as representative. The
two North Carolina counties, for example, show results entirely opposite from those anticipated on the
basis of the physiographic provinces involved. Tho
great proportion of poorly drained land in Bertie
County accounts largely for the small percentage of
mature soils in this area.
'L'HE MIOBO·FLOltA AND 'L'HE SOIL FAUNA
The influence of these environmental elements
upon the major soil divisions or the great soil
groups is not known in sufficient detail to warrant
any generalization having an important bearing
upon this study. Although numerous investigations
upon the nature and general results of the work or
micro-organisms upon soils have been carried on,
they have not been conducted extonsively and sys~
tematically with reference to any soil groups, and in
43
THE PEDALFERIC ENVIRONMENT
TABLE I-PERCENTAGE OF MATURE SOILS IN SELECTED
COUNTIES
Area
Pmiryerths ;
Marshall County, low2. .....
Dakota County, Neb .......
Major Type of Land
Form or Physiographic
Province
Approximate
Percentage ZI
of Mature
Soils
Till Plains ............
Loess Hills ...........
82.8
42.2
Podsols:
Aroostook, Me............ New England Uplands.
Ontonagon County, Mich.. , Superior Uplands ......
59.2
88.0
Gray-brownerihs;
Miami County, Ohio ....... Till Plains ............
Tompkins County, N. Y .... Appalachian Plateau ...
52.1
20.9
Red-and-Yellowerths:
Bertie County, N. C ....... Coastal Plains ........
Guilford County, N. C ..... Piedmont ............
62.7
Ferruginous Laterites:
Pierce County, Ga •. " ..... Coastal Plains ........
Lake County, Fla .......... Coastal Plains ........
26.0
50.2
14 9
only a few instances with regard to the morphological features of the profile.22
21 U. S. Dept. Agri., Field Opcl'ations, Bureau of Soils, 1918, p.
1116; 1919, p. 1690; 1917, p. 25; 1921, p. 87; 1916, p. 16 j 1920,
p. 1585; 1918, pp. 173-174; 1920, p. 180; 1918, p. 495; 1923, p. 416.
22P. E. Brown amI T. H. Benton: Microorganisms in Some Soil
Profiles in lawn, Proe. and Papers First Int'!. Congo Soil SCi.,
Com. III, pp. 100-106.
44
THE PEDALFERS
SIGNIFICANT ORARACTERISTIOS
The pedalfers occupy those sections of the United
StaLes in which the active environmental inLluenC'C's
and the dominant soil forming processes are prevailingly degrading. Compared with tht, petlocals,
which are derived from identical or essPlltially ('qui-valent materials, the mature peclnHcl's have passed
through processes of devE'lopnwut which have deprived them of a large part of their fertile constituents and left them physieally inferior, as far as
agricultural relationships are concerned, to their
coordinate division. As soils, they arc the POOl'Pl'
of the two groups, although cortain oHuw t'lwirollmental features with which they aro associat('d have
made them the more productive soils in spite of
their inferior prollerties.
CHEMIOAL PROPERTIES
Broad Effect of Climate and Vegetation.-As
stated on a previous page, the environment under
which the pedaHers have evolved has beon fmch that
it maintained the soil and parent material in a predominantly moist condition to great d('pihs. This
is obviously a primary result of the nbundunt precipitation (at least 25 to 30 inches annually). It is
also due, however, to the character 0 f the natural
vegetation, the forest formation.
A forest formation, according to Russian investigators, produces under its foliage a hydl'othermical
regime very different from that effectrcl by tho her-
SIGNIFICANT CIIARACTERISTICS
45
baceous growth of the pedocals. 23 In view of the
better preservation of the snow covering (in regions
having this form of precipitation) and of the lower
degree of evaporation under the shade of the leaves
and forest bedCling/4, the upper horizons are subject
to greater moistening. Under these circumstances
and the high rainfall, materials upon which the fertility of the pedalfers depends are to a greater or
less degree carried out of the soil and lost in the
drainage waters. This removal has not only taken
place during the process of evolution of the soils but
continues to take place as soluble materials are
formed through fUTther decomposition.
The Chemical Profile.-The maximum loss of material occurs in the A horizon, which, because of this
deprivation, is called the horizon of maximum extraction,2G although substances are also removed
from the B horizon, the horizon of concentration. 20
In this manner a chemical profile is developed, the
composition of the two horizons being markedly unlike at maturity. The extraction and concentration
are brought about in part through eluviation 27 (the
mechanical transfer of material), in part by transfer through solution and reprecipitation (chemically), and in part by both processes. 28 Fine
Neustruev: op. cit., p. 23.
Ibid.
25 C. F. Marbut. Outline of a Sellemo for the Diffilrentiation of
Soils into Mapping Units on a Uniform Basis for all Countries,
op. oit., p. 263.
20 Ibid., p. 262.
27 ReI)ort of Committee on Terminology, Soil Terminology, op. cit.,
p. 31.
28 Marbut: op. oit.
23
2;\
46
THE PEDALFERS
grained materials, clay and silt, are mechanically
transferred from the upper to the lower horizons.
"Along with the mechanical transfer of material
there is also some chemical transfer consisting of a
removal of sesquioxides, alkalies and alkaline earths
and organic. matter." 29 The percentage of iron
and alumina decreases in the A and increases in the
B horizon,30 this feature being one of the distinguishing characteristics of the pedalfers. (See Table
II.) "Not necessarily all the material, either that
removed mechanically or that removed chemically
from the horizon of extraction, becomes concentrated in the horizon of accumulation," 31 however.
As the bases are freed by decomposition, they are
carbonated by percolating waters carrying carbonic
acid,32 taken up in solution and removed from the
soil; B3 hence the characterization, non-lime-accumulating, as the removal of calcium carbonate in these
soils contrasts so strikingly with its accumulation
in the pedocals. Not only have the carbonates,
formed as a result of the process of carbonation,
been carried away, but also those" originally present in the material from which the soil was developed have been removed from both the upper horizon and the horizon of concentration." 84 In many
Ibid.
Ibid.
51 Ibid.
S2 E. Ramann: The Evolution ana. Classification of Soils (English
Translation by C. L. Whittles), Beffer, 1928, pp. 14-15.
58 C. F. Marbut: The Contribution of Soil Surveys to Soil Science,
op. cit., p. 131.
34 C. F. Marbut: Outline of a Scheme for the DifferenUation of
Soils into Mapping Units on a Uniform Basis for all Countries,
op. cit., p. 262.
20
50
47
SIGNIFICANT OHARACTERISTICS
TABLE II-OHEMICAL ANALYSES OF REPRESENTATIVE
MATURE PEDALFERS
(Complete Analyses)
Gn.\ Y-llllOWNlilllTB:
(Eo.etern MarYland)
PODBOL
(N orth Central Michigl1n)
Horizons
Hori ..ons
OONSTITUENTS
Alo
Per
Cent
SiO, ...... 58.99
T i0 2.. ···· 0.75
4.50
Fe20a .....
AhOs.··· . 13.00
MnO ...... 0.18
1.57
CaD ......
MgO ...... 1.30
K,O ...... 2.15
N'BO ..... 1.18
P, 6 •••• ·· 0.17
SOa.····· , 0.12
Ignition
loss .... , 16,53
B,
A2,
Per
Cent
Per
Cent
C,
Per
Cent
A2,
AI'
Per
Cent
----- --- --73.00 65.02 53.14 87.83
0.41
0.76
5.34
3.38
12.0B
16.63
0.172 0.18
1.42
1.03
1.05
1.06
2.48
2.71
1.07
1.20
0.17
0.01
0.08
0.05
0.66
5.26
14.62
0.14
7.00
3.72
2.19
1.01
0.11
0.06
0.34
1.76
3.92
0.006
0.24
0.14
1.62
0.16
0.03
Per
Cent
0.29
0.34
2.25
10.58
0.01
0.74
0.20
1.97
0.44
0.08
5.70
11.20
Total. .. 100.44 100,20 100.22
0,074 0.12
N ....... · 0,44
0.05
8oul"ce: lVI, Baldwin. Some Characteristio
Profiles of the North Ccntml States, Amer.
Soil Survey Assn., Bull. VII, Vol. I, p. 125.
C,
Per
Cent
--_
----90.57
80.74
82.03
1.11
4.77
0.006
0.16
0.14
1.1l2
0.06
0.00
0.02
0.05
3.87
1,45
--_ --- --_ --- ----100,27
99.11 99.97
3,1}4
B,
Per
Cent
0.D6
-
3.67
101.14
0.29
2.25
8.57
0.006
0.76
0.20
2.07
0.42
0.07
0,07
3.01
--99.7311
Source; L. L. Les, et aI" Soil
S urvay of Trenton Area N, J .,
U. S, Dept, of Av;rie" Field 0rerations, Bureau of Sana, 1921, p. 588.
n.l!lDElHTH
(South Carolina)
The atriking features of
these profiles are the rela-
Hori.zollS
tive concBntro.tionl3 of ir.on
OONS"ITCENTS
Ab
Per
Cent
A2.
Per
Cent
B.
Per
Cent
C,
Per
Cent
--- --- --- - - ----Bi02.· .. · . 84.34 86.15 52.03 56.33
TIO•.. , ...
Fe20a···· .
AI 2 0,., ...
MnO"".
OaO ..... ,
MgO ......
K20 .. , ...
N'i3 0 .....
PE) 5 . . . . . .
B 3.......
Ignition
loss .....
0.42
1.24
0.02
0.53
1.37
1.56
7.12
9.23
5.05
6,33 25,55 24.24
0.047 0.032 0.044 0.054
0,12 Trum1 Trace Trace
0,01
0.42
0.83
0.08
0.64
0.77
2.02
1.10
0,42
0.42
0.39
0.39
0.03
0.03
0.11
0.12
0.03
1).03
0.03
0.01
7.48
4.18 10.32
8.47
--- --- - - ---
Total ... 99,96 100.08 100.49 100.50
N ........ 0.119 0.042 0.02
0,005
Source: W, D. Lee and S, F. Davidson,
Soil Survoy of Polk County N. C .• U. S.
Der.t. 01 Agrio., Field Operations, Bureau of
Soi ., 1923, p. 339.
and alunlinD. in the B
horizons as compared to
the A hmizon and the C
horizon ~he ~nrent maI.rlal).
n t to podsol
for example, the Iron and
alumina content of the B
horizon is 5.34 sud 16,63,
respectively, whereas the
i':{r:~:pxn~agc ~~W;~~:~:
relatively lower. Thegencral deorease in alkuU.B
and alkaline earths in
upper, as compared with
lower, horizons iB also
charftcteriatic. Note the
higher nitrogen oontent in
the B horizon of the podsol; tho 0,44 per ocnt of
the Al horizon i. largely
raw humua.
-
48
THE PEDALFERS
cases, moreover, "the removal of carbonates has extended into the horizon beneath both of these," 55
the C horizon.
In general, however, the C horizons have had no
noticeable removal or accumulation. This horizon
is "the original geologic material that has suffered
no change except such as has accompanied disintegration and decomposition, if the rocks were originally consolidated, and leaching of carbonates and
some other constitutents. It is the horizon in which
the processes of weathering have not caused concentration of any kind by transfer from overlying horizons. No differentiation into textural horizons has
been produced in it through soil-making processes,
such variations of this kind as may be found in any
particular place being due to original geologjc conditions. " 56
The Chemical Impoverishment.-As a result of all
these processes, the pedalfers are relatively impoverished soils. They have lost a significant part of the
materials originally present in the parent formations.
Their content of soluble mineral maUer-especially
the significant potassium, calcium, and phosphorus
-is low. They have gained some organic matter
but the increase is small. "Roots of trees have a
long life so that they contribute only a trifling amount
to the organic matter of the soil, the supply of dead
residues being furnished almost exclusively by the
leaf-fall at the surface of the soiL" 31 In the podJl51bid., pp. 262-263.
116
87
Thia., p. 263.
Ramann: op. cit., :po 41.
SIGNIFICANT CHARACTERISTICS
49
sols, this material merely accumulates on the surface
as raw humus or is deposited in rather moderate
quantities in the B horizon, where it contributes
comparatively little to the soil's productivity. The
gray-brownerths, red-and-yellowerths and the ferruginous laterites have a thin surface mantle of
mold which .is intermingled to a sman extent with
the upper part of the A horizon, but under cultivation this is soon lost or much reduced in quantity.
As a whole, therefore, the pedalfers are deficient in
all the chief limiting nutrient elements,:lS both organic and inorganic. Owing to the loss of bases,
moreover, they are acid in reaction. They possess,
.in short, the less desirable chemical features. Although the parent materials ,vere rich in those elements making for high fertility, they have been deprived of these materials and reduced to soils of
relatively low fertility.
PHYSICAL CHARACTERISTWS
Physically, the evolution of the pedalfers has also
not been in the direction of acquiring those features
deemed most desirable in connection with man's use
of the soil. Although the soil-forming processes
have in some cases improved the physical condition
of the original parent material, such as that effected
in the thorough weathering of dense intractable
clays, the resulting characteristics of the soils considered as a whole are not commensurate with those
which the mature pedocals have acquired.
88 T. L. Lyon and II. O. Buckman: The Nature and Properties of
Soils, p. 10.
50
THE PEDALFERS
Texture Profile.-The pedalfers have a well-developed texture profile. Owing to the relative concentration of coarse constitutents in the A hori~wns by
the removal of fine materials, and the accumulation
of such materials in the B horizons in the process
of soil development,89 the latter have become prevailingly heavier textured than the former. In the
finer textured soils, such as the loams of Ohio and
Indiana, for example, the B horizons are heavy clay
loams. 40 Even sandy soils, like the Sassafras sandy
loams of the Coastal Plains, have acquired heavier
textured subsoils:H
Disadvantages of the Textu~'e Profile.-The prevailing textures of the pedalfers are not of the prollounced coarse salldy types, with the notable exception of the Coastal Plains, parts of the Appalachians
and Lake States, and other more limited areas. A.
very large number are loams and silt loams. For
these the loss of uniformity of texture in the development of the texture profile and the acquisition of
heavy textured subsoils means an unfavorable decrease in their penetrability. The freedom of root
range of the B, as compared to the A, horizons is
restricted, the increased proportion of fine textured
material, clay and silt, deterring their movement:12
The ability of this horizon to absorb water is likewise diminished. When exposed to erosion, thereMarbut: op. oit., p. 262.
Baldwin: op. cit., p. 127.
41 U. S. Dept. Agr., Field Opel'ations, BUl'eau of Soils, 1919, p. 493.
42 S. P. Kravkov: Aehievements of Russian Seience in the Field
of Agxicultural Pedology, Russian Pedological Investigations IX,
p. O.
39
40
SIGNIFICANT CHARACTERISTICS
51
fore, the decreased absorptivity of the heavier B
horizons, especially when imperfectly weathered/3
increases the susceptibility of the A. horizons toward
Temoval. The surface layers reach the sat11l'ation
point and slide or slump to lower levels. The normal
mature soils are not poorly drained, however, as
the internal drainage is capable of removing all surplus water; they are merely resistive to movement.
On the other hand, the author has observed that soils
with well-developed texture profiles are slightly
"colder" and "later" in spring than those with imperfect profiles, the difference relating in part probably to the less rapid drainage of the heavier subsoil.
Advantages of the Texture Profile.-Although
the acquisition of a texture profile has been disad.vantageous to the pedalfers of heavy texture, it is
economically beneficial to those of coarse texture.
Sandy soils are easy to work, are well drained, and
warm up early in spring. They are consequently
prized for truck and garden crops. Owing to the
fact that they are thoroughly leached, however, they
require heavy fertilization. Being coarse in texture,
they take up water more readily and are more impoverished than their associates of heavier texture
in which the degree of removal of soluble materials
has been proportionately less. (Compare in this
connection even two sandy soils of slightly different
texture, the Lakewood sand and fine sand.) 44 On the
48 R. H. Bennett: The Geographical Relation of Soil Erosion to
Land Pl'oductivity, Geogr. Rev., Vol. XVIII, 1928, p. 590.
44 U. S. Dept. Agr., Field Operations, Bureau of Soils, 1921, pp.
1625-1626.
52
THE PEDALFERS
other hand, the fact that in maturity soils of even
this character acquire subsoils of heavier texture
than the surface horizons improves not only their
water holding capacity but it also checks the rapid
loss of fertilizers when these materials are applied
to them under cultivation. In the case of such soils,
then, the acquisition of a texture profile has been
advantageous, although in the majority of pedalfers
its development as such has generally been somewhat detrimental.
Structure Profile.-Soil structure refers to the
natural arrangement of the individual particles
(clay, silt and sand) of which soil material is composed, as larger aggregates or bodies. A variety
of forms are assumed-granular, nutty, blocky,
columnar, cylindrical, spheroidal, laminated, lenticular, etc.4,5 Their genesis are the results of soilmaking processes, this physical feature being one of
the more striking soil characteristics.
The structure profile of mature non-sandy pedalfers is in general well defined. The A horizons have
a simple structure, the units being either sjngle
grained or soft imperfect aggregates of small diameter. The B horizons possess a compound structure,4G the masses forming comparatively large
angular agglomerations of irregular size and
shape. 41 These range up to about 25 mm. in diameter, the size usually increasing with depth. They
45 J. C. Russell, L. B. Olmstead, and B. H. Hendrickson: Forms
of Soil Structure, Amer. Soil Survey Assn., Bull. X, pp. 120-133.
40 Ibid.
H Baldwin: op. Ilit., pp. 124, 127. W. E. Hearn: Southern Soils,
Amer. Soil Survey Assn., Bull. VII, Vol. I, pp. 17, 19, 20, 22.
SIGNIFICANT CHARACTERISTICS
53
comprise the so-called nutty structures typical of
forest soils. No general statement can be made with
reference to the structural properties of the C hori~
zons, owing to their variable nature. As a whole
they appear to be without structure or it is only
incipiently expressed.
. Significance of Structure.-The development of
structure is not only most clearly manifest but also
reaches its maximum economic importance in soils
of heavy texture. In such soils its significance exceeds that of all other properties. Heavy textured
soils of poor or imperfect strncture are hard and
refractory when dry, plastic and intractable when
wet, and form lumpy, cloddy surfaces when turned
in plowing. Their natural drainage is poor and they
are unresponsive to fertilizers. Roots and air penetrate them with difficulty.
Soils with good structure, on the other hand, form
smooth crumbly seedbeds, the upturned masses
breaking down readily along the cleavage planes of
the structural particles. If the aggregates are well
developed and resistive to disintegration and destruction, even clayey soils, popularly classed as
heavy and refractory, crumble like sandy soils and
have all those non-coherent properties associated
with loamy types. 48 Such soils, moreover, have good
internal drainage, as water easily penetrates the interstructural air spaces. As the majority of crops
require well-drained soils, the disposition of surplus
water is necessarily important.
48 S. A. Zakharov. Achievements of Russian SCience in Morphology
of Soils, Russian Pedological Investigations II, p. 21.
54
THE PEDALFERS
The relationship of good structure to fertilizution
is of equal, if not greater, significance. Infertile
soils with favorable structure may be profitably fertilized since they possess the physical characteristics
favorable to plant occupation. Soils with poor structure, however, are unresponsive and, contrary to
prevailing belief, cannot be made productive by the
mere addition of proper fertilizers. In fact, good
structure in heavy textured soils is more important
than the presence of potash, phosphorus and other
so-called plant foods; more important than any
chemical or physical property, since it appears to
be extremely difficult, if not impossible, to correct,
especially over large areas:i9
Soil material of sandy texture usually has a simple structure or the structure is only "feebly expressed"; 50 but the deficiency is economically unimportant, as the grains are not strongly adhesive
and the soils are tractable. This textural class is
naturally very friable and possesses good internal
drainage. In view of the physical condition, moreover, most sandy soils are responsive to fertilizers.
Evaluation of the Structure Profile.-Economically, the simple structure of the A horizons is disadvantageous, especially when compared with the '
granular structure of the prairyerths and blackerths. The aggregates are not resistant to destruction and tend to break down under cultivation. On
the other band, the nut-like structure of the B horizons, although inferior to the granular arrangement
49
50
Wolfanger: op. cit., pp. 95-96.
Zakharov: op. cit., p. 15.
SIGNIFICANT CHARACTERISTICS
55
of the dark colored soils mentioned, has been a favorable acquisition. Where well perfected, it offsets
in no small degree the adverse features attained in
the formation of the texture profile. It increases
the subsoiFs penetrability, thereby enhancing its
drainage, root range, aeration and other phenomena
dependent upon free movement.
Lacking this structural development of the B horizons, most normal mature pedalfers of heavy texture would be impossible to cultivate. The deficiency is a condition impracticable to correct on any
large scale, as the B horizons are virtually inaccessible. The effect of unfavorable structure in the A
horizons may to some extent be offset with proper
cultivation, such as plowing under correct moisture
conditions, but it is improbable that similar correctives could be extensively applied to B horizons of
imperfect structure. Under limited conditions-for
example, certain hardpan soils of Cuba 51-they
have been successful. Fortunately, normal maturity
in pedalfers is accompanied by the development of
moderately good structure in the B horizons with its
beneficial effects upon the otherwise unfavorable
. texture profile of the soils.
COlor Profile.-Soil colors, as in most objects, are
not open to direct interpretation. Outside of leading to identification, their chief service is as indicators of other properties, such as drainage conditions
and organic matter content. "Uniformly colored
brown, yellow or red subsoils are characteristic of
development in situations that are well drained and
51 H. H. Bennett and R. V. Allison: The Soils of Cuba, pp. 6-7.
56
THE PEDALFERS
free throughout the true soil profile from the presence of ground water. The whole thickness of the
soil has lain above the level of the permanent water
table. Gray colors [except in normal podsols and
grayerthsJ or mixed colors indicate complete or
partial water logging of the soil or subsoil during
the period of development. With certain exceptions
. . . the relative content of organic matter in soils,
usually in the upper part of the surface horizon,
is indicated by the relative darkness of the soil
color." 52
The principal basic colors of the pedalfcrs are
red, yellow, light brown and gray-that is, they are
light colored soils, and the colors are usually tinted,
shaded or "mixed" (light red, dark gray, yellowish
brown, etc.). The soils are not mottled, however,
but are uniformly colored. Although this is an obvious characteristic of all normal mature soils, it is
a significant relationship feature, as it connotes adequate drainage and most crops require well-drained
soils for optimum growth conditions.
The color profile is well defined. With the exception of the podsols, it consists typically of: (1) a
thin surficial dark colored layer of leaf mold; (2) a
slightly dark colored upper A horizon darker than
the remainder of the profile, as more decayed organic matter has been incorporated with it; (3) a
grayish, brownish, yellowish or pale reddish lower
A horizon; (4) a lighter colored brown, yellow or
red B horizon; and (5) a C horizon of any color,
depending upon the nature of the drainage and
5Z Marbut
and Manifold: 0p.. cit., p. 431.
THE PRAIRYERTHS
57
parent material. There is thus a gradual decrease
of darkness in color with depth. Although the organic matter content of the upper mineral horIzon
is highest, the amount, as stated in the section on
chemical characteristics, is small, and it is soon lost
under cultivation.
In the podsols the lower part or the raw humus
surface layer is but very slightly, if at all, commingled with the upper mineral horizon which in
these soils is gray 53 and the lightest in color of all
horizons. The B horizons, owing to the accumulation of organic matter by deposition, are the darkest. Hence the soils are in a sense inverted as
compared with most soils in which the humus layer
is the upper mineral horizon, but the podsols are
normal soils and should not be regarded as abnormal or unnatural.
THE PRAIRYERTHS
The prairyerths, as noted on a preceding page,
contrast so strikingly with the typical pedalfers that
it appears advisable to consider their significant
features and environmental characteristics collectively and apart from their allied groups.
THE OONTRAST WITH THE LIGHT OOLORED PEDALFERS
The climate of the prairyerths is such that the
soils should develop general characteristics similar
to their co-groups. The only feature of great mo53
Veach: op. oit., pp. 350-351.
58
THE PEDALFERS
ment which they possess in common with the soils
of their major division, however, is a negative characteristic-the absence of a zone of lime accumulation. Unlike the normal pedalfers, they are dark
brown in color and their content of nitrogen is high.
As regards mineral constitutents, they are not
markedly leached of their alkalies or alkaline earths.
Although some material has been transferred from
the A to the B horizons, the latter are not heavy and
the texture profiles are not well defined. The subsoils are finer textured than the surface zones but
the contrast is not as pronounced as it is in the corresponding horizons of the light colored pedalfers.
Eluviation and the chemical transfer of material
have becn unimportant. They are low in lime but
almost neutral or only slig11tly acid in l'eaction. The
soils have a compound but fine-granular structure,
the units forming cube-like aggregates of small diameter. In brief, their chemical and physical characteristics are those attributed to highly fertile and
productive soils. They do not have the perfection
of blaclmrths, their western neighbors, but they are
unexcelled as humid soils.
THE CLIMATIC, GEOLOGIC AND TOPOGRAPHW ENvmON·
MENT
The climatic, geologic and topographic environment of the prairyerths deviates in no essential respect from .that under which the typical pedalfers
have evolved. The average monthly temperature
range lies within the same limits as those attained
by the other pedalfers, and the precipitation varies
THE PRAIRYERTHS
59
from 25 to 40 inches annually. This amount is adequate to maintain a predominant downward movement of water extending to the water table. Under
this condition the calcium carbonate formed in
woathering or present in the parent material is
carried out of the soil, as in the case of all pedalfers,
and the soils are non-lime-accumulating. TIle parent formations, moreover, include loess and glacial,
as well as non-glacial, materials-accumulations
derived from limestones, sandstones, and shales. 54
The land forms embrace hill country, plains and low
plateaus, with extensive areas of smooth, welldrained land on which normal soil development can
take place.
THE NATURAL VEGETATION
Prairie Grasses.-The macro-floral environment
exhibits the chief contrast with that of the light
colored pedaIfers. It is universally tall grass.
Prairie grasses also form in part the natural vegetation of the neighboring blackerths but they constitute the typical plant association of the prairyerths.
This grass explains the dark color of the soils.
The large amount of black organic matter derived
from the decay of grass roots is intimately mixed
or combined with the mineral constituents of the
soil. 55 The vegetation also accounts for the other
unusual chemical and physical features noted.
G4 U. S. Dept. Agr., Field Operations, Bureau of Soils, 1914, pp.
2036-2037; 1921, pp. 1139-1140.
65 Rice: op. ait., p. 11.
60
THE PEDALFERS
Mingled with the prairyerths in both the northern
and southern part of their major belt of distribution
are light colored normal pedalfers derived from
similar parent materials, u6 but the natural vegetation of these soils is generally forest. Owing to the
precipitation, both the light colored and dark colored
groups are progressively losing their lime and other
soluble constituents, but the grass roots in the
process of growth apparel1tly lJring back at least a
part of the leached materials in solution and after
decay re-deposit these substancos 'in the soil mass.
This tends to maintain the original chemical make-up
and the properties dependent UpOll it. In the case
of the forest soils, material is also returned in solution, but the leaf litter merely accumulates on the
surface, where it decomposes and is incorporated
with the soil to only a slight extent. 57
Relationship of Prairyerths to Pedalfers.-It is
not improbable that the amount of soluble material
returned by the grass roots to the upper from the
lower horizons in any given period is less than that
removed throngh leaching. Trees, moreover, being
able to maintain themselves on the freshly exposed
soil material, in competition with the grasses, are
invading the region along drainage lines. 58 With
topographic maturity it is not unlikely, therefore,
but that the region will in the course of time become
forested, and the soils be degraded to normal pedal66 U. S. Dcpt. Agr., Field Operations, Bureau of Soils, 1918, pp.
792-793; 1924, pp. 12r--13.
61 Ramann: ap. cit., p. 43.
58 U. S. Dcpt. Agr., Field Operations, Bureau of SoilS, 1922, p. 318.
THE WESTERN PEDALFERS
61
fers. At all events, this is the condition in the
eroded areas where forest associations have secured
a foothold. 50
Considered with respect to their possible ultimate
development as normal pedalfers, the prairyerths
are immature soils.oO As they owe their character to
a dynamic factor, the grass vegetation, however,
pedologisis arc inclined to regard them as virtually
coordinate with the other great pedalferic soil
groups. They have developed under normal environmental influences and are fully adjusted to all
the factors of this environment. Furthermore, in
view of their extensiveness and critical geographio
significance, they cannot be ignored.
THE WESTERN PEDALFERS
It has already been stated that the profile of the
western pedalfers is similar to that of the principal
continuous l)odies of the eastern part of the United
States. In view of the rolling topography, it is
probable that a noteworthy part of these soils is
immature, however. This is also true of those occupying relatively level areas, such as parts of the
Puget Trough, where the soils are imperfectly
drained,ol and the flood plain floor of the California
Trough.o2 In fact, in so far as the matter has been
Ibid.
Ibid., 1920, p. 380.
61 Ibid., 1922, p. 1692.
62 Ibid., 1913, pp. 2320-2321; 1915, p. 2610; 1916, p. 2453; 1911,
p. 2564.
59
60
62
THE PEDALFERS
ascertained, it does not appear that a very large proportion of the pedalfers under cultivation in tho
West are mature soils, with the exception of local
situations. The aggregate area of mature soils
seems to be comparatively large but much of the
land is still forested or merely cut~over.6a
68 Compare, for example, Soil Survey of CIa kamas County, Oregon,
U. S. Dept. Agr., Field Operations, Bureau of Soils~ 1921, pp.
1633-1701.
CHAPTER III
THE PEDOClALS
The pedocals are, without exception, western soils.
Unlike the pedalferic group, they are not developed
in both divisions of the country. The principal unbroken body which lies east of the Rocky Mountains,
moreover, is considerably smaller than the corresponding member of the pedalfers. West of the
Great Plains the continuity is to a great extent interrupted by extensive areas of rough stony land
and local developments of pedalfers. For convenience in drawing broad generalizations, these included areas are ignored. Their presence is understood and their distribution may be ascertained on
the map.
THE PEDOOALICl ENVIRONMENT
OLIMATE
Precipitation.-In the sense that the pedalfers are
"humid" soils, the pedocals may be designated as
"semi-arid" and" arid" soils. The maximum mean
precipitation under which they evolved is about 25
inches annually, decreasing in parts of the Inter63
64
THE PECODALS
montane Plateaus to approximately 5 inches.1 It
has been so low that" the soils . . . have been developed under conditions of a moisture supply insufficient to maintain a continuous downward movement of moisture to an indefinite depth." 2
Unlike the typical pedalfers (the pedalfers exclusive of the prairyerths), the variation in the total
precipitation has been a vital factor in bringing
about important differences among the pedocals.3
Its decrease from east to west, disregarding the
mountains, is well known. Ranging from the upper
to the lower limits of precipitation, it has given rise
to the four north-south belts of great soil groups,
the blackerths, chestnuterths, brownerths and grayerths, respectively. Although the differences in rainfall between any two groups is small, it is apparently highly significant. At any Tate, the soils corresponding to such differences are quite dissimilar.
From the standpoint of precipitation, then, the
blackerths are "sub-humid" soils; the chestnuterths, " semi-arid"; the brownerths, " sub-arid" ;
and the grayerths, "arid."
TemJlerature.-The average monthly temperature
range is about the same as that of the pedalfers.
The July limits are approximately 65° F. and 90 0
F., and the January, 00 F. and 55 0 F.4 As in the
case of the pcdalfcl's, the differences in temperature
have brought about the formation of unlike groups
1 J. B. Kincer: Atlas of American AgricultUl'e, l'm't II, See. A,
pp.6-7.
2 Marbut: op. cit., p. 2G3.
II Bennett and Allison: op. cit., PP. 351-352.
4. Ward: op. cit.
THE PEDOCALIC ENVIRONMENT
65
within the major division. These groups form several east-west belts trending at right angles to the
north-south belts conforming to the variation in
precipitation, the intersections outlining a rough
gridiron pattern. 5 As adequnte data with respect to
all the fundamental features 01 the east-west belts
of soils, particularly as one differ::; from the other,
is not yet available, their significance to this study
cannot be determined, and their distri1)ution is not
indicated on the map. They are regarded as merely
expressing differences in degree within the northsouth belts (the blackerths, etc), such as depth of
color of surface and subsoil horizons. 6
NATURAL VEGETATION
The natural vegetation of the pedocals is most
briefly described as non-forest. The plant associations are prevailingly grasses but there are also plant
communities of savannah, brush and shrub. 7 With
the chief exception of extensive areas in west-central
Texas and parts of Montana, the prevailing vegetation in the principal body east of the Rocky Mountains is grassland communities.s The predominant
plant communities of the blackerths are tall grass in
the eastern and short grass in the western part of
their area of distribution, with mesquite savannah
5 C. F. Marbut:
A Scheme for Soil Classification, op. cit., l?p.
23-25.
(l C. F. Marbut:
Soils of the Gmat Plains, op. cit., pp. 47-66.
7 Shantz and ZOll: op. cit., pp. 15-26.
8 H. L. Shantz:
The Natural Vegetatioll of the Gl'eat Plains,
Annals Assn. Amer. Geogrs., Vol. XIII, No.2, 1923, p. 83.
66
THE PEDOCALS
of local importance in Texas.1I The typical vegetation of the chestnuterths and bl'ownerths is short
grasses, the density of the cover of the latter being
less than that of the former. The rainfall under
which the grayerths developed is so low that it is
incapable of supporting grasses, but maintains an
open shrub growth of sagebrush and creosote bush.1o
In general, therefore, the density of the vegetative
cover decTeases from blackerths to grayerths.
PARENT MATERIAl.s
The parent formations of the pedocals, like those
of the pedalfers, include a wide range of materials.
There are unconsolidated deposits of highly calcareous glacial accumulations, lacustl'ine deposits, allu~
vial fan and plain materials, marl and chalk, loess,
sands and clays; there are also l'esidual accumulations derived from sandstones, shales, limestones,
and crystalline rocks.l l The largest proportion of
the soils have been evolved from accumulations
from sandstone and shale, alluvial fan and plain
material, and loess deposits, areally impoTtant in
about the order named.
In conformity with the pedalfers, the relationship
of the parent materials to the mature pedocals as a
group is of minor import. Regardless o,f the nature
D U. S. Dept. Agr., Field Operations, Bureau of Soils, 1922, pp.
2066, 2073.
10 Shantz and Zon: op. cit., pp. 21-25.
11 U. S. Dept. Agr., Field Operations, BUl'eau of Soils, 1910, pp.
889-896; 1911, pp. 1214-1217, 1913-1919; 1918, pp. 1515, 1519;
1919. pp. 1728-1731; 1920, pp. 871-873; 1921, pp. 721, 947; 1923,
THE PEDOCALIC ENVIRONMENT
67
of the original formation, each has a zone of lime
accumulation and such other features as charactcrize the normal mature soils of the major division.
N or may any of the great soil groups be exclusively
identified with any of the unconsolidated deposits or
residual accuumlations named above.
LAND FORMS
As brought out in the chapter on pedalfers, the
major land fOTms aTe chiefly significant as determinants of degree of development, well drained plains
and plateaus possessing the greater propoTtions of
mature soils. Topographically, the pedocalic zone
is of interest in the extent of its mountainous land
on which soil development has taken place only
locally, and the large ratio of high plateaus,J.2 Where
rainfall, in Tesponse to altitude, is adequate, and the
vegetation, forest or prairie grasses, the soils of
these highland areas are members of the pedalforic
division.~3 In general, however, these soils, and the
pedocltlic groups developed under corresponding
conditions, have not been carefully studied and
mapped, and most of them are indicated on the
map as rough broken land without reference to the
character of the soils. Although there are widespread belts of hilly areas, this type of land form
is much less extensive than in the pedalfeTic zone.
Fenneman. op. cit., pp. 328-353,
U. S. Dept. Agr., Field Operations, Bureau of Soils, 1918, pp.
1565-1570.
12
13
68
THE PEDOCALS
SIGNIFICANT CHARACTERISTICS
Although certain features of the pedocalic environment bring about the removal of soluble materials in the evolution of the soils, the loss is small and
the process of development, in contrast to that of the
pedalfers, should not be described as degradational.
Chemically, the mature soils have retained practically all the soluble substances upon which fertility
depends, although there has been some transfer of
materials from one horizon to another. The physical features are also such that the soils present no
significant or unusually difficult problem in cultivation or management. In short, they have attained
all those features which" good" soils possess.
CHEMICAL PROPERTIES
Broad Effect of Climate and Vegetation.-As
stated above, the low rainfall under which the
pedocals develop is such that soil material is maintained in a continuous moist condition to only limited
depths. In fact, this is the most striking and significant general environmental difference or influence affecting the evolution of the major soil divisions. When the moisture column is unbroken to
the water table, materials extracted by solution are
subject to complete removal in the drainage waters.
When the continuity is interrupted, these substances
are deposited in the lower zone of penetration, the
depths depending upon their nature, that of the soil
material, and the rainfall. In the first instance, the
less soluble materials are deposited at higher levels;
THE PEDOCALIC ENVIRONMENT
69
in the second, the depth of penetration is naturally
greater in soils of coarser textures; in the last, the
quantity of precipitation determines the amount of
moisture available for the process.
In contrast to the natural forest vegetation of the
pedalfers, the herbaceous associations of the pedocals have been effective in offsetting, to an important degree, the leaching effects of the precipitation. "The roots of herbaceous growth are usually
distributed in the upper portion of soils; they remove the ashy elements from the deeper layers, and
raise them to the soil surface, enriching the upper
portion of soil with ashy elements, and thereby
paralyzing the decrease in bases effected by hydrolysis in the mineral portion of soil; this results
in soils under meadow vegetation being much more
saturated with bases than those under forest vegetation. The meadow vegetation, which does not provide as great a protection against evaporation as the
forest-crown, favors a higher intensity of capillary
processes in dry seasons enabling soil solutions to
rise to the surface and evaporate, thus neutralizing
to a certain extent the results of water percolation
occurring in humid seasons. This has a similar effect resulting in a decrease in the degree of unsaturation of soil, and in the degree of acidity of the soil
solution. " 14
Ohemical Profile.-The development of the pedocalic profile is effected both by eluviation and the
transfer of material through solution and chemical
reprecipitation, although the "mechanical transfer
1;1,
Neustruev: op. cit., pp. 23-24.
70
THE PEDOCALS
of fine-grained material from the upper part of the
soil and its accumulation in the lower" J." does not
always take place.
The roost significant movement in the pedocalic
processes of soil evolution is the transfer of alkalies
or alkaline earth salts, usually lime carbonate, from
the A horizons, and their accumulation in the B
horizons.J.6 Not only are the soluble substances
named originally pr€lsent in the parent material subject to such removal, but also such carbonates as are
formed in the weathering of calcium-bearing minerals_"7 On the other hand, in view of the effect of
the herbaceous vegetation just noted, the upper horizons are generally not deficient in the mineral
sol,utes essential to plant growth.
Although alkalies and alkaline earth salts are removed from the upper and deposited in the lower
horizons, only the calcium carbonate appears to accumulate to any noteworthy extent. During periods
or cycles of higher rainfall to which these regions
are subject, the more soluble salts appear to be
either retransferred to great aepths or are carried
out in the drainage waters. .At any rate, chemical
analyses do not indicate their unusual and consistent
concentration in the B horizons. (See Table III.)
The carbonate accumulation varies both in depth
and in form. Owing to the differences in precipitalG
C. F. Mal'but: Outline of a Schome for the Differentiation of
Soils into Mapping Units on a Uniform Basis for all Countries, ap.
cit., p. 263 .
•6
l7
Ibid.
C. F. Marbut: The Contributiou of Soil Surveys to Soil Science,
ap. cit., p. 133.
71
THE PEDOCALIC ENVIH.ONMENT
TABLE III-CHEMICAL ANALYSES OF REPRESENTATIVE
MATURE PEDOCALS
(Complete Analyses)
Data-Courtesy U. S. B1lreau of Chemistry and Soils
BLACKERTH
CUESTl>!UTERTH
(Central Nebraska)
(Eastern Wyoming)
Horizons
Horizons
CONSTITUENTS
A"
Pel'
Cent
A2,
Per
Cent
B
"
Per
Cent
B z,
Per
Cent
AI,
Per
Cent
A~,
TI,
Per
Cent
Per
Cent
C,
Per
Cent
- - -- - - - - - - - - - -
SiO z ...... 71.73 71.87 71.58 70.14 71.81 65.54 65.09 68.87
Ti0 2 •••••• 0.55 0.53 0.54 0.55 0.62 0.54 0.51 0.53
Fe 20a ..... 2.78 3.10 3.25 3.43 3.29 3.18 3.07 2.89
Al,Oa ..... 11.34 12.60 12.72 12.53 12.15 11.49 11.19 9.78
MnO ..... 0.05 0.05 0.05 0.04 0.06 0.05 0.04 0.05
CaO ...... 1.68 1.56 1.52 3.41 1.96 5.99 6.71 5.31
MgO ...... 0.84 1.03 1.18 1.60 1.57 1.70 1.81 1.65
K 20 ...... 2.51 2.68 2.82 2.81 2.11 2.46 2.46 2.60
NazO ..... 1.04 1.07 1.00 0.98 1.62 1.46 1.50 1.77
P 20 •...... 0.20 0.19 0.21 0.22 0.49 0.34 0.38 0.34
80 3 •.••.•• 0.02 0.02 0.02 0.02 0.04 0.03 0.02 0.05
N ........ 0.19 0.10 0.05 0.03 0.10 0.09 0.05 0.03
In contrast to the pedalferic profile (Table II, page 47) there is
no perceptible increase in iron and alumina in the B horizon of the
pedocals. The percentage of alkalies, alkaline earths and phosphorus, moreover, is comparatively high. Note the concentration
of CaO in the B horizons.
72
THE PEDOCALS
tion, it tends to reach its average maximum depth,
other things being equal, in those parts of the blackerth belts in which the soils are maintained in the
most moist condition, and its minimum depth in the
driest parts of the grayerth regions.1B In state or
form, the carbonates range from finely divided material, through soft and hard concretions, to indurated caliche, the latter being largely characteristic
of many of the southern pedocals, but also of certain
northern grayerths. 19
Unlike the pedalfers, there is no noticeable accumulation of iron and alumina in the B horizons.
The removal of these substances takes place only
under prevailing acid cOllditions,2o and the pedocals
are in general nearly neutral or alkaline in reaction.
The prevailing chemical reaction, therefore, is of
supreme importance in determining the ultimate
course of development of the chemical profile of any
soil and its acquisition of the broad pedocalic or
pedalfel'ie features.
Although the herbaceous natural vegetation of the
pedocals is insignificant as regards volume, in comparison with the great amount of organic material
involved in the forest associations of the pedalfers,
the normal pedocals are in general better supplied
with nitrogen. The proportion naturally varies
with the character and the density of the cover. The
organic debris, moreover, does not accumulate
c.
F. Marbut: Soils of tho Great Plains, ap. cit., pp. 46-66.
Latham, op. cit., pp. 34;-40.
:20 B. Aarllio: tIber die Ausfaliung des Eisenozyds und der Tonerdo
in :finnllindieschen Sand und Griiboden. Geotekniska Meddelanden
No. 16, Finland Geol. Survey, 1915.
l.S
l.91biil., pp. 56, 66.
THE PEDOCALIC ENVIRONMENT
73
merely as raw humus on the surface, as in the podsols, or as partially decomposed organic material
commingled with the upper A horizon, but it forms
an important and intimate part of the soil mass.
The fine fibrous roots permeate the upper soil horizons completely, are l'elatively short-lived, and at
death slowly decompose within the soil body.21 The
humus formed, moreover, possesses a higher degree
of dispersion and is of entirely different character
from that formed from the ligneous material of the
tree roots. 22
In general the pedocalic processes may be designated as quasi-aggradational. Strictly interpreted,
the soils have lost, as well as gained, material, but
the losses are negligible and in contrast with the
pedalfers they are essentially unleached. The proportion of soluble mineral matter is comparatively
high and they have gained a significant amount of
organic substances. They have a moderate to high
content of lime, potash, phosphorus and nitrogen.
While all but the nitrogen were present in the original paTent material, the inorganic constituents were,
with unimportant exceptions, insoluble. In the evolution of the mature soils, a certain proportion has
been rendered soluble and Tetained in the soil mass.
The change from an insoluble to a soluble state has
consequently been a significant gain, and the qualification, quasi-aggTadational, is properly descriptive
of this condition in contrast with the almost wholly
degTadational pedalferic processes. In the latter
21
22
Rnmallll.: op. cit.
Neustruev: op. cit., p. 23.
74
TilE PEDOCALS
processes the mature soils have lost a very large
part or practically all of their soluble materials and
have been "enriched" only by the relative concentration of iron and alumina through the removal of
the soluble materials.
PHYSICAL PROPERTIES
In physical properties, the pedoeals also rank as
soils par excellence. Certain old soils have llardpans, others are alkali or salty and certain young
soils are relatively intractable, but the normal mature soils are in general well adapted to the utilizations which associated environmental conditions impose upon them.
Texture Profile.-The texture profiles of the
normal pedocals are not well marked. There has
been some concentration of fine textured materials
in the B horizons through decomposition within the
horizons and transfer from the A horizons, but the
difference in texture of the surface layers and subsoils is small. The latter are but slightly heavier
textured than the former. In siht, a certaiN. horizon
of some soils may appear to be heavier than the surface horizons, but the chief diversity is one of relative compaction, not texture, and such horizons have
been designated as the zones of maximum compaction. 23
From the standpoint of utilization of the soil, the
profiles of the normal pedocals do not present the
2a F. A. Hayos: Revision of the Grundy Series of Nebr!1ska, Amer.
Soil Survey Assn., Bull. IX, p. 87.
PHYSICAL PROPERTIES
75
unfavorable features of the pedalferic types. Bccause the difference in texture between soils and
subsoils is slight, root, air and moisture penetration
are easy, and the soils offer no mechanical problem
of import under cultivation comparable to that of
the pedalferic pronle. They are subject to erosion
of headwater drainage, for, in spite of the absorptivity of the B horizons, the latter are not always
capable of removing the surplus water as rapidly as
it accumulates. The sandy soils are likewise subject
to eolation, but neither type of erosion, water or
wind, is related, in a significant degree, to tho character of the profile.
Structure Profile.-The pedocalic structure profiles, like the texture profiles, are also not strikingly
developed. In so far as this morphological characteristic has been studied, it has not shown the pronounced differences existing between surface soils
and the subsoils that exist in the pedalfers. The
structure of the upper and lower horizons are not
alike but the divergence is not as great as in the
average light colored pedalfers.
As a whole, the structure of the American pedocals
is to a great extent not well known, with the broad
exception of the blackerths and parts of the ohest~
nuterths. On account of the high content of bases,
particularly lime, the soil material of heavy texture
is in general well flocculated, ;however, and thus is
easily worked when brought under cultivation. A
noteworthy feature, moreover, in so far as the matter has Eeen observed, is the resistant character of
the micro-structural aggregates. While the macro-
76
THE PEDOCALS
aggregates (compound structures) assume various
forms in the virgin soils, the small structural masses
formed under cultivation are remarkably durable.
They apparently do not disintegrate rapidly, the
soils remaining tractable after relatively prolonged
cultivation.
Although pedocals, ill contrast to pedalfers, retain
their structure for extended periods, it has been
observed by European investigators that even the
blackerths eventually lose their granular structure
or in time it becomes markedly modified.24 However, "they recover their natural granular structure
when left untouched for a certain period of time." 25
It is not known, at least it does not seem to have
been reported, whether other pedocals are subject to
like modiflcations but it does not appear improbable
that they also undergo such changes, although presumably varying in rate and method. On the other
hand, it is well known that the alterations which all
normal pedocals mayor may not undergo is unimportant in comparison with the critical transformations brought about in pedalfers under cultivation.
The blackerths, like the prairyerths, have the most
perfect strncture of the various great soil groups
comprising the pedocalic divisions. It is even superior to that of the prairyerths. It should be noted,
however, that the difference in structure in its bearing upon tilth is of far less importance than the
difference between the prairyerths and the normal
pedalfers.
op. oit., p. 22.
Kravkov: op. oit., p. 6.
24 Zakharov:
25
PHYSICAL PROPERTIES
77
While the general structure profile of the normal
pedaHers includes simple-structured, more or less
deflocculated, A horizons and nutty-structure B
horizons (with their associate advantages and disadvantages), the prevailing pedocalic profile appears to be one in which the soil particles are well
flocculated, and both horizons have a compound
structure. The structure of the A horizons of the
blackerths is typically fine-granular, and the B
horizons, coarse-granular. The structure of the
corresponding horizons of the chestnuterths is
fragmellta1 2G (so-called cloddy) or roughly columnar and columnar, respectively.27 The structure
of the brownerths, as far as known and reported,
has already been described (page 31). Glinlm
states that the structure of the equivalent Russian Brown Earth is identical 'with that of the
Russian Ohestnut Colored soils. 28 In the graycrths,
the" desert crust" or "desert pavement" is underlain by the open porous "desert mulch" and this in
turn passes into material of rough columnar
structure.
Color Profile.-The fundamental pedocalic colors
include black, dark to light brown, gray, yellow and
red, and, like the peclalfers, are usually tinted,
shaded or mixed and not mottled. Yellow and red
are chiefly the subsoil colors, although appearing at
the surface in young or eroded soils and cultivated
areas.
Russell: op. cit.
C. F. Marbut: Soils of tho Great Plains, op. cit., pp. 58-64,
and personal observations.
28 Glinka: op. oit., p. 146.
26
27
78
THE PEDOCALS
Unlike the previous physical profiles considered,
the color profile of most of the grassland soils is
better marked and more strongly differentiated.
Owing to the accumulation of humus in the upper
horizons, they are distinctly darker than the lower
horizons. The difference is particularly noteworthy
in tbe case of the dark colored surface soils and
grayish, yellowish or reddish zones of carbonate accumulation. 29 In general, the profile consists of
three major divisions: (1) a relatively dark colored
surface soil, the darkest of all horizons, (2) a lighter
colored upper subsoil which is yellowish, brownish
or reddish, and (3) the still lighter colored zone of
accumulation. In contrast to the normal pedalfers,
the dark organic content of the A horizons is not
rapidly lost under cultivation.
The most striking color variation in the pedocals
is the gradual decrease in the depth of color of the
surface horizons from north to south and in any
latitude from east to west either within a great soil
group or in the case of adjacent belts.BO The northern blackerths are darker than the central and
southern subdivisions, and there is a similar gradation from blackerths to chestnuterths, brownerths
and grayerths. The east-west change expresses the
decrease in humus and the decline in precipitation in
the direction mentioned; the north-south change is
an expression of the increase in temperature and its
effectiveness in oxidizing the organic matter.
29 U. S. Dept. Agr., Field Operations, Bureau of Soils, 1917, p.
1823; 1919, p. 1125; 1921, p. 721.
80 Marbut: 0'1. cit., p. 46.
MINOR PEDOCALIC BELTS
79
In the grayerths group, the sparso, open character
of the vegetative covering has not been favorable to
the accumulation of a relatively large amount of
black humus compounds, and the color pronles do
not show the marked contrasts of dark colored soil
and light colored subsoil. In the southern Nevada
desert, for example, the A horizons are light brownish gray with a pale reddish tint, the upper B horizons ught brownish gray, and the lower B horizons
gray.al
MINOR PEDOCALIC BELTS
Although the descriptions drawn, as in the case
of the pedalfers, have referred directly only to the
main soil belts of the Great Plains province and the
great body of grayerths of the Intermontane Plateaus, the characterizations given are likewise applicable to the corresponding soil groups of the
Walla "Walla Plateau, the California Trough and
similar areas west of the Great Plains.82 Marbut
calls the former "another Great Plains in miniature." 33 The pedocals of the California Trough,
on the other hand, are chiefly old soils,S<! the area
occupied by mature members being inconsiderable.
Latham:
Marbut:
83 Ibiil., p.
34 Latham:
31
22
op. cit., pp. 32-40.
op. cit.
45.
op. cit., pp. 26-31.
CHAPTER IV
GEOGRAPHIC RELATIONSHIPS
GENERAL PRINCIPLES
HUMAN ACTIVITIES DEPENDING UPON THE SOIL
Of the several major types of adjustments which
men have made to the natural environment of the
United States, nie soil environment shows its most
direct and manifold relationships to the agricul"
tural, pastoral and nemoricultural (forest culture)
groups. These groups include nearly all the leading activities in which the character of the soil may
conceivably most immediately affect the nature of
the adjustment. Although other industries and
various social and political matters may also be influenced to some extent by the nature of the soil
environment, yet the soil's bearing upon these phenomena is either largely indirect or of but minor
consequence. Accordingly, in endeavoring to ascertain the more significant geographic relationships of
the great soil divisions, only the more basic types
of adjustments first named will be contemplated.
What are these relationships and how may their existence be discovered?
80
GENERAL PRINCIPLES
81
AREAL CORRELATIONS
It is a well recognized principle of geographic
research that potential relationship between a given
environmental element and a human phenomenon
is suggested by the approximate coincidence of their
respective areas of distribution. Such concurrence
does not establish the relationship but it directs attention to the possibility of its existence. Thus the
frequent occurrence of moderate to dense populations in plains and sparse populations in mountains
has long been regarded as an indication of the general favorableness of plains and the unfriendliness
of mountains to human occupation, although many
plains and mountains similarly eligible for such relationships by no means conform to the generalization j 1 likewise, the general restriction of certain
crops to certain climates is considered evincive of
the influence of such climates upon the crops, in
spite of the fact that such crops are widely distributed and are grown in important quantities in many
other climate types. 2 In both instances, the approximate congruence of the areas of distribution of the
phenomena under consideration intimates the possibility of relationship, although it does not demonstrate its actual existence. Such a qualification
must be measured by other criteria.
The real existence of a relationship depends
necessarily upon the character of the phenomena
E. C. Semple: Influences of Geographic Environment, pp. 473 ff.
Cf. V. C. Finch and O. E. Baker: Geography of the World's
Agriculture, U. S. Dept. Agr., 1917.
1.
2
82
GEOGRAPHIC RELATIONSHIPS
concerned and the nature of their association. Uuless the environmental element possesses some attribute of consequence to the human feature under observation and the attribute actually functions, there
will, obviously, be no relationship. The fact that
plains possess smoothness which facilitates population movement and agglomeration gives validity to
the conclusion that sllch land forms are favorable to
man, whereas the prevalence of slopes in mountains,
which impede activity, confirms the unfriendly relationship of such topography. Were the surface configuration of these land forms of no significance to
man, relationships would needs be non-existent.
Applying tue principles just enunciated to investigations in soil geography, one may discover in a
similar manner the existence or non-existence of
relationships between the various soil groups and
the basic soil adjustments noted on an earlier page.
For example, when the area of distribution of a
given adjustment, or the plant life associated with
that adjustment, is consistently in essential conformity with the area occupied by a given group of
soils, the conformation may in general be interpreted as indicative of relationships between the two.
The reality of relationship, similar to the land form
illustration, depends upon the nature of the adjustment. Unless the soils' characteristics are of significance to the adjustment, the relationship is
merely one of accidental similarity in distribution
and of inconsequential geographic import.
GENERAL PRINCIPLES
83
SOIL VS. CLIMATE, LAND FORMS AND NATURAL
VEGETATION
Owing to the fact that several major environmental factors other than soil, notably climate, land
forms ana, in some cases, natural vegetation-aU of
which may be essential to the existence or a given
adjustment-occupy approximately the same area,
the application of the principles of areal distribution
must be attended with due regard for several important considerations.
In the first place, it should be borne in mind
that although each clement involved participates in
the evolution of the adjustment, and may form an.
integral part of the equation, it manifests its relationships, regardless of their importance, in conformity with its own characteristics-climate in accordance with its thermic and hydric features, land
form in agreement with its surface configuration,
soil with regard to its physical, chemical and biological properties, and vegetation with respect to its
biological attributes. Therefore, while given types
of climate and land forms may also have been factors in bringing about a given adjustment, and their
areas of distribution conform with that of a given
soil group, there need be no confusion as to their
relationships, since the pedologic are of an entirely
different order from the climatic and topographic.
In the second place, the genetic affiliations of the
soils should be carefully distinguished from, and
recognized as but incidental to a study of, their attributive relationships. The soil groups are the
products of certain types of climate, land forms and
84
GEOGRAPHIC RELATIONSmpS
vegetation, and all these have approximately the
same distribution as the soils, but their bearing upon
the evolution of the soils is a matter very distinct
from the influence of the soils upon a given crop or
adjustment. The soils' relationships are those expressed through their O'wn inherent attributes, and
are quite apart from the genetic kinships of these
attributes. The influence of a factor giving rise to
a particular characteristic may be highly significant
in the evolution of that featul'e, but when the soil's
response is exhibited in accordance with that feature, it is the soil and not the parental factor which
displays that reaction. Consequently, although the
soil, tnrDl1gn the operation of various forces, acquires certain properties-a condition of leaching
and soil moisture, a given chemical Teaction, etc.its geographic characteT should be gaged or accredited in terms or those reatUTes and not in terms of
the climate or some other indirect factor which
played an important part in their development.
Such factors are not of direct concern in the relationship. Due regard may be given them at the
pleasure of the investigator, and the factors may
also operate directly other than through the medium
of the sOlI, but the point here insisted upon is one
of proper recognition of their 'Place. Ne.glect in
recognizing the differences in such relationships and
carrying the application of this philosophy to its
logical conclusion tend to relegate all geographic inquiries to a deliberation of the relationships between
the few ultimate physical, chemical and biological
forces upon which the evolution of environmental
GENERAL PRINCIPLES
85
features rests. These matters seem obvious but
they are particularly stressed because of the not
infrequent failure of geographers to distinguish
carefully between them.
Although each of the soil groups shares the environmental influences with certain types of climate,
etc., and the relative importance of each associate
element varies with different circumstances and
types of human activity, it is not the primary purpOse of this investigation to set forth the geographic
attributes of these elements nor to determine their
comparative significance. The first regard is that
of discovering and setting forth the soils' relationships. The influences of the other factors are recognized and have been given due attention by other
investigators, and it is felt that continuous reference
to their relationships would soon encumber the
reader with ",veIl-known qualifications. Only very
brief statements of the more essential of such inter~
relationships have therefore been incorporated. Nor
has resolute effort been made to determine their
significance as compared with that of the soils.
Quantitative relationships-for example, whether
climate, land form or some other environmental
factor is of major significance in "determining" a
given adjustment-are subjects of considerable
debate among geographers, owing largely to tnc
character of their original preparation, but this
study is not undertaken with the view of ascertaining the soil's relative importance in such connec~
tions. Although facts and conclusions bearing upon
such relationships are included, they are primarily
86
GEOGRAPHIC RELATIONSHIPS
introduced in the hope of Iurtller elucidating the
qualitative relationsl1ips.
AGRICULTURAL ADJUSTMENTS
The more strilting relationships between the several soil divisions and the agricultural adjustments
of the United States may be ascertained by comparing and analyzing the distribution of the soils with
two significant agricultural phenomena: (1) the
distribution of land under cultivation, and (2) the
distribution of the principal cultivated crops. The
first study gives a perspective survey of the comparative utility and serviceability of the soils for
cropping in general; the second gives the specific
bearing of the soils upon the chief crops produced.
LAND UNDER CULTIVATION
As is well known, the use of land for cropping is
primarily dependent, environmentally, upon a favorable combination of three major elements, climate,
soil and land forms. Although all are essential
factors, climate is obviously of greatest general importance, owing to its widespread continuity and
intangible character. Without adequate rainfall
and length of growing season, land will not be
brought under cultivation, irrespective of propitiousness of soil and land form.
Given a favorable climate, soil, rather than land
form, is in general the leading determinative as to
land cultivability under nmmal conditions, since a
surface configuration amenable to cultivation is not
AGRICULTURAL ADJUSTMENTS
87
infrequently mantled with unproductive soils which
mayor may not respond to amendments economically. Even where the terrain is steep and rolling
but the soil productive, the adverse topographic features are in no small measure disregarded, as the
voluminous literature on soil erosion everywhere
testifies. It should Df! recognized, on the other band,
that extreme declivity in land forms does constitute
a factor limiting cultivation in the ordinary sense
of the term, yet such areas are also lacking, as a
whole, in suitable soils.
The Major Soil Divisions: Status of Oultivated
Land in the Two D'ivisions.-In comparing the
area of distribution of the major soil divisions with
the land under cultivation, it is apparent that the
pedalfers (including the prairyerths) comprise the
principal agricultural soils of the United States.
Their area of distribution includes the largest proportion of land in harvested crops within the country.3 Outside the northern and southern margins
of the major eastern body, there are few extensive
tracts, viewed in a large way, which do not include
some crop land. Although few states wholly or almost wholly within the zone have more than 50 per
cent of their land under cultivation {Iowa, 60, Illinois, 55, in 1925)4 and the lower range includes
states with only 5 to 10 per cent in crops (Florida,
6, Maine, 9, in 1925)5 the aggregate area of such land
3 Cf. O. E. Baker: A Graphic Summary ot American Agriculture,
U. S. Dept. Agr., Yearbook, 1921, p. 424; O. E. Baker: Agricultural
Maps, U. S. Dept. Agr., Ymlrbook of Agriculture, 1928, p. 642.
4 United States Census of Agriculture, 1925, Part II, pp. 7-8.
5 Ibid., pp. 6, 10.
88
GEOGRAPHIC RELATIONSHIPS
in the entire pedalferic zone considerably exceeds
that of the pedocals. It is estimated that the pedalferic share is about 70 to 75 per cent. Unfortunately, for statistical studies, state boundaries do
not correspond to natural regions, and the states
whose soils are prevailingly pedalferic-those east
of the North Dakota-Texas belt-include only approximately 57 per cent of the total crop land in the
United States. s Roughly adjusting the figures to
thld areas occupied by pedalferic soils, however, it
appears that about three-fourths of the land in cultivation is in this major division.
The pedocalic division includes enormous areas
almost devoid of cultivation. There are nearly a
dozen large states with less than 10 per cent of their
area in crop land (two states, Arizona and Nevada,
with less than 1 per cent.r On the basis of the previous estimate made for the pedalfers, only about
25 per cent of the crop land in the United States is
pedocalic.
Relationship of Pedalfers to Land under Gultivation.-Although the difference in the proportion of
land between the two major soil divisions is primarily one of favorableness of rainfall, in view of
its control over the soils' moisture content, and
trends logically in this direction, the soils stand in
opposite relationship. The pedalfers, outside the
prairyerths, are the poorer of the two soil divisions.
When regarded from the standpoint of their fea~
tures as a whole, they have been an unfriendly
~ Ibid., pp. 4-13.
'l'Ibid.
AGRICULTURAL ADJUSTMENTS
89
rather than a favorable factor in accounting for
their position. Theil' chemical properties, particularly with reference to their relation to the plant
food supply and the soils' structure, constitute their
weakest economic features. When first brought
lmder cultivation they are very productive but the
natural store of soluble constituents has been so depleted in the course of their evolution that it is soon
reduced below the crops' requirements, and their
productivity declines rapidly. The low percentage
of organic matter and mineral plant foods become
"exhausted" and with impoverishment in chemical
constitutents comes decline in that important physical characteristic, tIle soil struchue.
The stronger features of the soils and the pedological properties upon which their extensive utility
chiefly rests are their high water content and moderately well-developed structure. Occupying tlle
more humid parts of the United States, their water
supply is in general dependable and adequate for
plant growth. Although their structural features
are inferior to those of the pedocals, and the aggregates tend to break down rather rapidly undel' cultivation, they are nevertheless of such a character
that they provide a remunerative basis for the
amelioration not only of their own circumstances but
also of the chemical condition of the soils. They
furnish a physical condition friendly to plant occupation and one upon which a large expenditure for
chemical fertilizers or the use of animal manure,
other things being equal, is profitable. Like dairy
stock of good conformation, they are responsive to
90
GEOGRAPHIO RELATIONSHIPS
intelligent treatment (crop rotation, etc.) and
proper nourishment (fertilizers). In token of this
fact are the several hundreds of millions of dollars
spent annually for commercial fertilizers alone.s
The application is by no means universal but the
number of farms on which at least some fertilizers
in some form are not used is probably not very large.
As the most important consideration in the use of
fertilizers is the physical condition of the soilssince soils with poor shuctuTe aTe to a great extent
unresponsive-it is a significant relationship, from
the pedological standpoint, that in general normal
maturity in non-sandy pedalfers, though marked by
a somewhat unfavol'able structure in the A horizons,
is accompanied by the development of moderately
good structure in the B horizons. Were the pedalfers largely immature soils of heavy, clayey texture,
undoubtecTI.y a much smaller percentage would be
under cultivation. Such, for example, is the case
in northeastern Texas, northwestern Louisiana,
southwestern Arkansas and the so-called Clay Rill
Belt of Georgia, Alabama and Mississippi, where
the grayish to reddish Susquehanna series with their
stiff, mottled clay subsoils predominate.o "The clay
is valuable only for pasture land and for hay and
timber." 10
The serviceability of the mature sandy textured
pedalfers, unlike those of heavy texture, lies, it will
8 Ibid., p. 16.
O. E. Baker: A GraphiC Summary of American
Agrieulttlre, op. cit., p. 496.
9 Bennett: op. cit., p. 103.
1'0 Ibid., p. 105.
AGRICULTURAL ADJUSTMENTS
91
be recalled, in the development of the texture profile
(page 52). The heavier textured, albeit sandy, sub~
soils tend to retard the excessive loss of fertilizers.
Sandy soils without such subsoils have in general
either not been brought under cultivation or they
have been rapidly abandoned.l l
The continued necessity of overcoming these soils
and modifying their unfavorable features to con~
form to more propitious associated conditions assigns them to the same general geographic category
as the vanquishment of topographic and climatic
barriers. Their utilization is attended by laborious
subdual rather than facile appropriation. As a
monument to the problems they have created stand
the numerous agricultural experiment stations in the
humid parts of the United States. Their perplexing
questions were closely associated with the inception
of modern pedology and the bringing into being of
the Bureau of Soils in the latter part of the 19th
century. In fact, most of the agricultural, geographic and other literature dealing with soils is
based upon, or largely devoted to, the difficulties
created by the soils of this division. Like the mountain barriers to transportation, men have worked to
remove their obstructions. Unfortunately, until re~
cently, so much of this effort was not guided by a
system founded upon a wholly scientific analysis
of the soils' significant features, limitations and
capabilities, and their problems and such solutions
as have been effected have been regarded largely
n U. S. Dept. Agr., Field Operations, Bureau of Soils, 1919, 1Ip.
414,503.
92
GEOGRAPHIC RELATIONSHIPS
as almost equally applicable to the wholly different
pedocals.
Relationship of Pedocals to L,and 'under Gultivation·.-The soils of this division present conditions
nearly opposite to those of the pcdalfers. In view
of the light precipitation, the position of soil and
climate is reversed. The pedocals offer apPl'oximately every pedological feature (except an adequate water supply) in general conceivably favorable to plant growth adapted to this region. Yet,
with partial exception of the blackerth belt, the average rainfall is too low for normal cropping, and,
unlike the chemical poverty of the pedalfcrs, the
deficiency cannot as a 'whole be made up. "Vater, on
the scale needed, is more costly than fertilizer. The
quantity required far exceeds the supply. When
locally available from surface or underground
sources, such as rivers and wells, the soilR, as in the
case of the application of fertilizers to pcdalfcrs,
yield crops quite in excess of their native productive
capacity, and densely populated agricultuml adjuRtments arc possible. The irrigable land, however,
is only a small fraction of the total area.12
It is nevertheless highly significant that such a
large proportion of the cropped land in the United
States occurs in the pedocalic zone-only about 5
per cent of the land under cultivation in the zone
is irrigated-where agriculture is handicapped by
uncertain inadequate precipitation. The extended
utilization must be largely ascribed, therefore, to the
character of the soils. Had the process of soil evo12
Cf. Bakel':
op. cit., p. 429.
AGRICULTURAL ADJUSTMENTS
93
lution been predominantly degrading, and the mature
soils developed as typical pedalfers, there can be
little doubt but that almost none of the soils would
have been brought under cultivation. The cost of
fertilizers, combined with the rainfall risk, would
make farming in general prohibitive. Under pres~
ent conditions, however, the soils are essentially Ullleached and their structure is such that they can be
cultivated on a large scale at low costs. The prepa~
ration of good seedbeds is simple. 'Vhen dry farming is practiced, the natural or cultivated structure
of the soils is an important asset to frequent cultivation. Water and air penetration, moreover, are
easy, the soils being absorptive of a large part of
the low rainfall. The content and proportion of
soluble plant foods and the physical condition of the
soils are those especially favorable to the crops climatically tolerant to the region. As the precipitation
is low, the soil solution is relatively concentrated,
and the plants may figuratively gorge themselves
with food. Furthermore, owing to the richness in
nutritive SUbstances, and its diminishing effect on
the magnitude of the transpiration coefficient, the
water requirements of the crops are perceptibly
decreased.
On account of the deficient rainfall, man's efforts
in this region have been largely in the direction of
plant rather than soil improvement. Drouth-resis~
ant grains, hay crops and tree crops are sought or
new varieties are bred. 13 Farm management is
chiefly concerned with capitalizing any small cli13
Cf. J. R. Smith: Tree Crops, pp. 69-80.
94
GEOGRAPHIC RELATIONSHIPS
matic advantage. Such attention as the soil receives
-fallowing, deep plowing, etc.-is in the direction
of offsetting the rainfall deficiency. In a published
summary of the work of the United States Dry-land
Field Station, Ardmore, South Dakota, from 1912
to 1925, for example, but one fertilizer experiment,
green manuring, is recorded, and it was concluded
that the practice was not necessary in that region.
The other experiments were all concerned with crops
and methods of utilizing the inadequate precipitation more fully.
Although manure and occasionally chemical fertilizers have been applied to certain pedocalic soils,
their use as a whole, in SO far as experiments indi.
cate, have, unlike the pedalfers, met with little response. Theoretically, moreover, it appears that no
important increase in crop yields may in the known
future be obtained by this method.H The virgin
soils are moderate to high in all essential soluble
organic and inorganic substances except phosphorus, ana the proportion of this mineral substance
is higher than that which prevails in typical pedalfers. The application of additional material, therefore, is in the main merely giving to the soil that
which it hath.
The Great Soil Groups: The Pedalfers.-:A.lthough
the major part of the land under cultivation in the
United States is· pedalferic, the distribution of this
land within the zone is quite varied. The prairy14 C. F. Marbut: The Rise, Decline ana Revival of Malthusianism
in Relation to Geography ana Character of Soils, Annals Aesn.
Amer. Geogrs., Vol. 15, 1925, p. 27.
AGRICULTURAL ADJUSTMENTS
95
erths possess the most of such land, and the podsols
the least, the relative ranking of the great soil
groups being shown in Table IV (A). The decrease
is not uniform, the first two embracing the larger
proportion. The red-and-yellowerths are intermediate, whereas both the ferruginous laterites and
podsols have a very small percentage of their soils
under cultivation.
TABLE IV-RELATIVE RANK OF PEDALFERIC GREAT SOIL
GROUPS ACCORDING TO PROPORTION OF LAND UNDER
CULTIVATION AND SOIL AND CLIMATE FAVORABILITY
(A) Land Uruler CuUivation Sequence
(1) Prairyerths
(2) Gray-brownerths
(3) Red-and-yellowerths
(4) Ferruginous laterites
(5) Podsols
(B) Pedologic Sequence
(1)
(2)
(3)
(4)
(5)
Prairyerths
Gray-brownerths
Red-and-yellowerths
Ferruginous laterites
Podsols
(C) Climatic Sequence
(1) Ferruginous laterites (humid tropic climate)
(2) Red-and-yellowerths (humid sub-tropic climate)
(3) Gray-brownerths and Prairyerths (long-summer-humidcontinental climate)
(4) Podsols (short-summer-humid-continental climate)
The climatic ranks are measured in terms of abundance of precipitation and length of growing season; the Boil, with reference to natural
fertility and perfection of physical features.
The difference in the relative proportion of land
in crops in these great soil groups tends as a whole
to be more nearly a function of soil than climate
(Table IV). Although the humid climate is the environmental factor primarily responsible for bringing the soils under cultivation, the relative position
96
GEOGRAPHIC RELATIONSHIPS
of the groups runs counter to the favorable secondary climatic differences within the zone but in the
same direction as the favorable changes in the soils.
This is true not only for the prairyerths and graybrownerths with the same climatic advantages but
also for all the groups except the podsols, whose
soils as well as climate are the poorest. With amelioration in character comes increase in cultivability
and responsiveness to comparable applications of
fertilizers. The more favorable the soils, the less
handicaps to overcome and the greater the proportion brought under cultivation. Outside the exception noted there is no instance in which the more
productive climate has the greater proportion of
cropped land.
The ptairyerths naturally occupy first position,
their granular structure, slight leaching and almost
negligible fertilizer requirements comprising their
most significant features. The well-developed structure, comparatively moderate degree of leaching
and moderate fertilizer requirements give the graybrownerths the leading position among the light
colored pedalfers. The red-and-yellowerths are
thoroughly leached; and this, combined with the
coarse structure, more deteriorative than that of the
gray-brownel'ths, serves to reduce them to a position
secondary to the latter group. The ferruginous
laterites are still more leached and largely sandy
soils, and their region includes considerable areas
underlain by organic hardpans.1. 5 In the podsolization process, almost all soluble materials are re15
U. S. Dept. Agr., Field Operations, Bureau of Soils, 1923, p. 415.
AGRICULTURAL ADJUSTMENTS
97
moved from the podsols, mineral decomposition is
slow, and they become markedly acid in reaction.
The Pedoe.als.-In the pedocalic zone the distribution of land under cultivation is much less uniform
than in the pedalferic areas. Not only do the blackerth and chestnuterth regions include the most of
such land in the division, but the former has the
larger share by a considerable difference.16 Very
little of the brownerths and grayerths is under cultivation. The latter regions embrace most of the irrigated lands of the country but the soils under
irrigation are prevailingly immature.
Ascribed to its more ultimate cause, the difference
in the proportion of land under cultivation in these
groups must be largely attributed to the westward
decrease in rainfall from hlackerths to grayerths.
Regarded from the soil standpoint, it corresponds
chiefly with the diminution in their water balance
and to a slight extent with a small decrease in favorability of other characteristics. Though highest in
the blackerths, the moisture content is seldom adequate to match the full productive capacity of the
soils. Yet, in spite of this limitation, the proportion
of land under cultivation is practically as great as
that of the prairyerths, the high fertility of the soils
and their ease of manipulation comprising an irresistible attraction. The chestnute1'ths are but
slightly inferior soils but their moisture content is
so low that it is just sufficient to sustain an agriculture consisting of a combined system of cropping
:16
Of. Baker:
op. cit., p. 642.
op. cit., p. 424; O. E, Baker: Agricultural Maps,
98
GEOGRAPHIC RELATIONSHIPS
and ranching in which the range, taking the region
as a whole, is of far greater importance. The gray~
erths and brownerths, being arid and sub-arid soils
respectively, are, with the exception of land capable
of irrigation, almost wholly pastoral.
PIUNOIPAL OROPS
The preceding pages have been concerned with the
relationships of the various soil groups to the land
under cultivation without reference to the crops produced. Such relationships rest upon more general
considerations than those of the latter because they
need have no regard for the peculiar requirements
of a crop. As man seems capable of finding plants
which will produce some sort of a crop irrespective
of soil and climate, the land under cultivation does
not necessarily reflect the tTUe harmony or discordance which may exist between that crop and its environment.
The production of a crop depends upon the same
general major environmental factors as those upon
which the use of land for cultivation rests, but each
is narrowed to more concrete types commensurate
with the plants' growth requirements. Climate of
necessity sets the outer growth limits on account of
its relation to precipitation and temperature maxima and minima. The conditions within such bounds
are by no means wholly optima, but vary from those
most favorable to those to which the plant is just
tolerant.
It is a well-known fact that within its climatio
regime the production of a crop varies enormously
AGRICULTURAL ADJUSTMENTS
99
-in the case of most crops from nil or practically
nothing to one or more centers of heavy production.
Such centers are of exceptional geographic interest
since they suggest the operation of unusual forces.
Though influenced to some extent by economic considerations, their locus is fundamentally a matter of
environmental circumstances. Either climate or
soil, or both, coupled with a favorable topography,
may in general be assumed to present conditions
especially advantageous to the production of the
crop in question.
In applying the principle of areal correlation to
determine the geographic significance of the several
soil groups to crop production, these centers are
given major attention. Owing to the dependence of
plant life upon soils, concurrence in distribution of
such centers and given soil groups is regarded as
conclusive evidence of important relationship. This
conclusion is accepted as confirmative even in those
cases in which the production of the crops takes
place on other soil groups. Its occurrence in such
situations is merely the outgrowth of other or additional relationships in the same manner as the development of dense populations in mountains, being
the result of ulterior or supplementary factors, does
not invalidate the generalization with respect to the
fundamental relationship between plains and population. The relationships may be accepted as prime,
moreover, especially when the production centers
are those of the first magnitude and have not attained this position by overcoming significant handicaps. Even when instances of the latter type occur,
100
GEOGRAPHIC RELATIONSHIPS
the relationships, though of a different order, may
be true and equally momentous, as the conquest of
barriers is a geographic phenomenon of import analogous to thnt of circumstances in which man's adjustments to his environment are favored by
friendly conditions.
The Major Soil Divisions.-Regarded in its entirety, the agriculture of the pedalfers is characterjzed by its wealth in crop variety and its extended
development of crop centers. The crop list includes
important representatives of nearly all the leading
crop groups of the United States-grains, fibers,
fruits, nuts, vegetables, roois, hays, etc.:t7 To detail
the individual crops would be to list practically
every significant type of crop grown in the occidental middle latitudes.
Although each crop, with inconsequential exceptions, is relatively widely dispersed within the zone,
the distribution in general is very unE-ven both of
acreage and of production. Each has a distinct
center of greater production, many possessing two
or more of such areas. Moreover, in the case of several crops whose areas of major production are in
the pedocalic zone there are noteworthy secondary
centers within the pedalferic division.18 Of the two
major soil divisions, the pedalfers represent by far
the greatest range in crops and crop groups, as well
as the proportion of land under cultivation.
The pedocalic zone, on the other hand, is distin17 Of. O. E. Baker: A Graphic Summary of American. Agriculture,
ap. oit., pp. 43H69.
18 Cf. ibid., pp. 440, 442, 443.
AGRICULTURAL ADJUSTMENTS
101
guished by the brevity of its crop list and the occurrence of the areas of major production of practically
all its principal crops within the division. There
are small acreages of many of the crops produced
in the pedalferic division but the leading crops are
grains and hays, the cereals far exceeding the forage group in both acreage and significance.19 .Although several of these crops are also grown in noteworthy quantity in the pedalferic zone, the chief production areas, with reference to the entire United
States, are included within the pedocalic division.
In view of their striking fundamental soil differences, it is patent that the crops of the two major
soil divisions, especially those of greater acreage
and production, should display some of the dissimilarities in character just noted. It is not immediately apparent, from the pedologic standpoint, however, why the naturally less fertile pedalfers should
possess the greater diversity. It would appear that
the poorer soils should have a more abbreviated
crop list.
As the relationships here involved are more comprehensible when reviewed with respect to the soil
groups, their analysis is referred to the section on
these units. In general the conditions are reflective
of the marked contrasts in the adaptivity of each
soil division and of the wide variation which each
climate type and soil group within the zones expresses.
The Great Soil Groups.-Taken as a whole, there
is a decidedly close concurrence in the area of dis19
Cf. ibid., pp. 438-449, 450, 4fi1.
102
GEOGRAPHIC RELATIONSHIPS
tribution of each of the great soil groups and one or
more of the leading crops of the two major soil divisions. Although none of the crops is confined to a
single soil group, just as no crop may be wholly associated with a given climate type but is grown under
widely varied conditions, yet the area of major production in the case of nearly every important crop
may be largely identified with one of them. Outside
such a soil group, the production is either almost
invariably attended by lower yields or, where of like
magnitude, determined by unusual local or special
circumstances, such as immature, less leached or
heavily fertilized soils.
The inclusion of the production centers of more
than one crop within a soil group is a common,
rather than unusual, occurrence. The relationship
is a very natural one, since soil groups, like climate
types, may be adapted to a variety of crops. The
exact locus of a center, as within a climate type, is
usually related to specific conditions within the
group, such as secondary differences in the soils, or
economic requirements.
The Prairyerths.-Though creative of marked
disparity in the pedalferic zone, the prairyerths
within themselves present a region of comparative
uniformity. Their agricultural complex includes but
few important crops, and these occupy comparatively large centers. Olimatically, the region is
suited to a larger number of crops but the soils are
well adapted to a limited variety only (ct. page 114),
Although corn and oats are grown in every great
soil region in the United States, and the climate
AGRICULTURAL ADJUSTMENTS
103
highly favorable to their production extends
through several of them,20 their area of major production is almost entirely confined to the northern
prairyerths 21 (roughly western Indiana to eastern
Nebraska). These soils form the heart of the" Corn
Belt. " Corn is one of the crops least tolerant to
unfavorable soil conditions; hence the high organic
matter content, the comparatively unleached condition of the soils, their granular structure and high
moisture content comprise the more significant pedologic relationships. As the crop is particularly
sensitive to drouth, the organic matter and granular
structure are important factors in maintaining the
moisture supply at its highest levels, yet at the same
time insure good internal drainage and aeration and
that [freedom of movement which its "remarkably
widely spreading, deeply penetrating, and profusely
branching root system" 22 requires.
Essentially similar relations characterize the oat
crop, although this grain appears to be even more
selective. At least, the area of distribution of its
major acreage is to .a very large extent restricted to
either mature soils slightly darker and less leached
and with a slightly higher water content than the
average within the region (Clarion, etc.) or to immature soils of analogous character.
Outside this belt of soils, the production and yield
per acre of these crops is in general relatively low
20 A. J. Henry, ct aZ.: Weather and Agriculture, U. S. Dept. Agr.,
Yearbook, 1924, pp. 503-510, 517-518.
21 Cf. Baker: op. at., pp. 435, 441.
22 J. E. Weaver: Root Development of Field Crops, p. 191.
104
GEOGRAPHIC RELATIONSHIPS
or moderate. The production of corn, for example,
in the gray-brownerth and red-and-yellowerth regions, both of which are as well adapted climatically
to corn as the prairyerths, is noteworthily lower,
acreage for acreage. During the year 1925, the yield
in Marshall County, Iowa, was 33 bushels to the acre,
but that of Frederick County, Maryland, in the
Shenandoah Valley, was 14; that of Maury County,
Tennessee, in the Nashville Basin, 21; and that of
Terrel County, Georgia, in the productive rederth
belt of southern Georgia, only 12 bushels. 23
In those instances where the extra-regional yields
equal that of the prairyerths, the production is due
to exceptional or local conditions. The more important of these are: (1) immature soils, such as
bottomland or artificially drained dark colored upland soils; (2) a small area in the blackerths of eastern Nebraska and southeastern South Dakota, the
soils of which are very similar to the prairyerths but
westward of which the favorability of the climate
for corn and oats decreases; and (3) mature soils
of other soil regions which have been fertilized, as
those of western Ohio. Being only of local or particular significance, these exceptions are of limited
consequence.
Agriculturally, the normal mature central and
southern prairyerths are comparatively unimportant. They comprise but a small portion of the soils
of this part of the region, the predominant members
being abnormal or immature. These age groups are
23 United States Census of .Agriculture, 1925, Part I, p. 863;
Part II, pp. 101, 743, 481.
AGRIOULTURAL ADJUSTMENTS
105
not under investigation in this study, but it may be
noted in passing that they are highly fertile; that
the Kansas group comprises the major center of
alfalfa production in the United States i M and that
the southern group forms the chief soils of one of
the major centers of cotton production (the black·
erths of Texas) and one of the more significant sec·
ondary centers (central Oklahoma) of this crop.25
The Gray.browne'rths.-The agriculture of the
gray-bl'ownerths is marked by diversity. It is characterized by its numerous crops and many small
production centers in contrast to the limited crops
and few large centers of the prairyerths. Climate
permitting, the region includes greater or lesser
areas of many of the important crops produced in
other regions. Some of these, such as clover,
timothy, tobacco and apples/ G occur largely within
the region, whereas others, particularly corn, wheat,
rye, oats and barley,27 are grown only in part, but in
either case the production centers are typically relatively small and scattered. There are few large
major centers, the chief feature of the agriculture,
apart from its crop heterogeneity, being its resolution into small production centers. The most extensive crop with comparatively large centers is hay.28
All the grain centers named are secondary, and the
areas of major production occur in other regions.
24
0/. Baker: op. cit., p. 451.
25 Ct.
Cf.
27 0/.
28 Cf.
26
ibid.,
ibid.,
ibid.,
ibid.,
p. 434.
pp. 446, 449, 465.
pp. 437, 440-443.
p. 447.
106
GEOGRAPHIC RELATIONSHIPS
:A. few centers, such as the sugar beet and field bean
section of Michiganr occupy abnormal soils.
The crop diversity of these soils is a reflection of
their great flexibility and moderate leaching. Like
all normal pedalfers, the gray-brownerths are very
productive when first brought under cultivation, and
decline, although less rapidly, with constant use
when not properly managed. Unlike their associate
groups, they are much more easily amended, require
much less fertilizer, and are much more productive
both naturally and when improved. Owing to their
moderate acidity, to the well-developed structure of
the B horizon of the heavy textured members, and
the texture profile of the sandier types, this improvement may, at relatively low cost, take a number of directions. The soils may be built up to meet
the peculiar requirements of a large number of
crops (page 114) and under intelligent treatment
can be made to produce, and in abundance, practicallyall the crops climatically adapted to the cool
middle latitudes. But this does not mean that they
comprise the "best" soils for such crops. They are
the soils which best lend themselves to preparation
for such crops. They are quite the converse of the
'Prairye:rths whose charaete:r and adaptability are
quite fixed.
The patchy character of the crop centra is related
to a variety of immediate conditions within the re~
gion. some of which are environmental, some economic. It is due in part to the scattered nature of
the areas of mature soils, as much of the region out2D
Ct. ibid., pp. 456, 457.
AGRICULTURAL ADJUSTMENTS
107
side the Till Plains has passed topographic immaturity. It is due in part to slight local differences
in the soils, each of which provides conditions to
which certain crops are somewhat better adapted.
This is illustrated by the tobacco crop of the limestone soils of Kentucky, the rye and potato crops of
the sandy soils of the Lake States, and the truck
crops of the North Atlantic Coastal Plain. Some
centers, such as the last one named, as well as the
large hay and dairy centers,BO occupying the broken
belt of mature soils extending from Troy, New York,
to St. Paul, }.fillnesota/1 are also determined in part
by climatic and in part by economic considerations.
The plasticity or the soils is one of their more remarkable features.
In the vVest the only extensive area of mature
gray-brownerths occurs in the Puget Trough, the
members of the California district being largely
young soils. The agriculture of the Puget Trough
is in part a duplicate of the dairy agriculture 32 of
the East, and in part has "the Corn Belt type with
the corn left out-general grain, grass, hay and livestock ,farming." sa The absence of grain corn in this
lowland is not due to the soils, however, because the
latter, it will be recalled, are similar to those of the
eastern part of the Corn Belt.s"
30 Of. C. V. Piper, et al.: OUT Forago Resources} Agr. Yearbook,
1923, pp. 330, 347.
31 Soil Map of the United States} by the author (unpublished).
32Piper, et al.: op. cit.; C. W. Larson, et al.: The Dairy Industry, Agr. Yearbook, HJ22, pp. 301, 304, 305, 324.
33 J. R. Smith: North America, p. 500.
34 U. S. Dept . .Agr., Field Operationa, Bureau of Soils, 19HJ, pp.
1846--1847.
108
GEOGRAPHIC RELATIONSHIPS
The Red-and-Yellowerths.-The red-and-yellowerth region, like the gray-brownerths, is one of crop
diversity, but the number of leading crops is somewhat smaller, and the major production centers tend
to be larger in size and fewer in number. The agriculture is largely one of considerable specialization~
chiefly cotton, tobacco, peanuts, sugar, rice, fruits,
etc.B5 Each crop is quite closely restricted to from
one to several centers, with the exception of cotton
which, ill addition to its centers, is with corn the general and cbaracteristic crop of the region.
These soils are similar to the gray-browerths in
their adaptiveness to a variety of crops but, owing
to their highly leached character, strong acidity and
the coarse deteriorative structure 01 the heavy textured members, their improvement and maintenance
in a productive state are much more arduous and
costly. Although the climate is favorable to numerous crops, the choice, in view of the poor soils, has
been inclined toward the more profitable and special
types (such as cotton), with ability to carry the fertilizer burden and with optimum climatic requirements better met by the conditions of this region
than any other. The disposition toward selection in
this direction has been particularly motivated by the
general philosophy of American agriculture-that
of producing a money crop-and the fact that the
soils as a whole are not well adapted to commercial
agriculture under American labor and soil standards. The continued application of ~arge amounts
85 Of. O. E. Baker: .Agricultural Regions of North .America, Part
II-The South, Economic Geography, Vol. III, No.1, pp. 50-83.
AGRICULTURAL ADJUSTMENTS
109
of fertilizer and labor-much more than the graybrownerths require-is prerequisite to their profitable utilization, a decided handicap when crops must
be sora, in competition with those prod1.1ced 011 soils
not so limited. Hence a more restricted list of important crops and a limit uti on to those of higher
commercial tenor.ail
As in every soil group, the production of each
crop has tended to adjust itself to the soils of the
region which best meet its peculiar pedologic and
economic requirements, and here the bodies of such
soils are relatively extensive and continuous. Unlike the gray-brownerth belt, comparative topographic immaturity still characterizes a large proportion of the area. As a result, the crop centers
are inclined to be larger and fewer in number rather
than small and dispersed, and their size is limited
chiefly by market conditions. Thus the recent increased demands for certain types of tobacco have
been met by expansion of the North Carolina area
on neighboring soils of character identical with
those of the older center instead of by the initiation
of new small centers elsewhere within the region.
The broad relationship of the soils to the crops of
the region is illustrated by the two crops of general
importance, cotton and corn. Both are grown on
86 On account of the impl}veriahed soils and their limited adaptation to commorcial agriculture, and espeeially in view of the tendency towards the migration of its chief money crops to other better
adapted soil regions, the red-and-yellowerth group-the first Boil
region to attain great commercial importanco in the United States
by means of its tobacco and cotton crops--may, in tho course of
time, be doomed to become a Bubsistence region.
110
GEOGRAPHIC RELATIONSHIPS
practically every mature soil group but the average
yield per acre is low. In the Piedmont and Upper
Coastal Plain district extending from North Carolina throngh South Carolina and Georgia, however,
the cotton crop is heavily fertilized, and the belt attains the rank of an area of major and heavy production. The expenditure for fertilizer here exceeds
that of any other crop in the United States. ar Corn,
on the other hand, having practically no commercial
value, receives essentially no fertilizer over any extended area within the red-and-yellowerth region,
except relatively small amounts, or such as is "left
over" in tlle soil from the cotton crop. Corn, consequently, has no center of major production in the
region, although its climatic adaptation is evinced
by its high yields, equal to those of the northern
prairyel'ths, when planted on fresh young bottomland soils.
The relationships of the leading crops of secondary importance in the region are similar to those
of cotton. Thus tobacco and peanuts, being profitable commercial crops, are heavily fertilized and
acquire large production centers. The rice and
sugar crop soils are non-mature and are therefore
not representative of the region.
The Fe1"Tt~ginous Laterites.-The pec1o-agricultural relationships of this group are very analogous
to those of the red-and-yellowerths. Although much
of the land under cultivation is abnormal-poorly
drained 01' underlain by organic hardpans-there
37
Cf. O. E. Baker: A Gmphlc Summary of .American Agriculture,
op. cit., p. 496.
AGRICULTURAL ADJUSTMENTS
111
are also extensive areas of normal well drained
soils which depict the more natural conditions of the
soil group.
In view of the humid tro:pic climate, the :potential
crop list is long and varied, but as the soils are
moderately to strongly acid and more highly leached
their ,fertilizer requirements are even greater than
equivalent soils of the red-and-yellowerths-thus
abbreviating the leading crops to those of proportionate high commercial value, principally early
vegetables and citrus fruits.:is So comparatively
narrow are the margins of profit, moreover, that the
fertilizer requirements of each individual crop are
observed with c0l1sidera1)le 1)l'ecision,3!) and due account is taken of the slightest local soil differences.
As in the red-and-yellowerth region, the maximum
yields are obtained not on the normal mature soils
but on the associated abnormal types. (See
Table V.)
TABLE V-POTATO YIELDS ON SEVERAL FLORIDA SOILS4G
Per Cent
Normal Mature:
Norfolk.... . . . . .. . . .... . . .. .. . ..
100
Abnormal:
Leon. . .... . . .... . ..... . . ..... ..
Blanton........................
St. Johns. . . . . . . . . . . . . . . . . . . . . . .
Portsmouth. . . . . . . . . . . . . . . . . . . . .
170
171
224
264
ss ct. Baker: op. oit., p. 53.
U. S. Dept. Agr., Field Operations, Bureau of Soils, 1923, p. 410.
«l J. H. Stallings: Soil Type and Crop Adaptation, Amer. Soil
Survey Assn., Bull. X, p. 75.
89
112
GEOGRAPHIC RELATIONSHlrS
The Podsols.-The agriculture of the podsols represents an adjustment to the least favorable regional soil and climatic conditions of the pcdalfers.
The summers are cool, the growing seasons short,
and the grayish soils highly acid and thoroughly
leached of practically all theil' soluble constituents.
.Although the proportion of mature soils is not high,
there are ,fairly extensive bodies of this age group
in northern Minnesota, Michigan and Maine.
A number of crops tolerant of the acid soils
and capable of maturing in the short cool growing
season may be grown, but the conditions of production are such that the majority are of a subsistence
character. The cost of meeting the fertilizer requirements is in general prohibitive. The region has
but one outstanding crop center, the well-known
Aroostook potato district, and this is maintained at
a cost of fertilization quite out of proportion to that
expended on the sandy gray-brownerths of the Lake
States to produce a comparable crop. (See Table
VI.)
TABLE VI-FERTILIZER EXPENDED TO PRODUCE ONE
BUSHEL OF POTATOES, 1925 41
Cents per
County
Bushel
Aroostook, Maine...... .... ......
15.1
Oaldand, Mich.. . . . . . . . . . . . . . . . ..
5.8
Montcalm, Mich.. . . . . . . . . . . . . . . .
1.8
Waupaoa, Wis...................
1.4
Hennepin, Minn.. . . . . . . . . . . . . . . .
4. 9
The Blackerths.-Turning now to the principal
agricultural group of the pedocals, the blackerths,
41 Data,
United States Census of Agriculture, 1925.
AGRICULTURAL ADJUSTMENTS
113
one finds a near summation of the restricted varietal
agriculture of the more fertile major soil division.
The agriculture of these soils is distinguished by the
striking similarity of its crops as regards type
(chiefly grains and hay), by its numerous extensive
and almost unbroken succession of major crop centers and the practical total absence of significant
secondary centers. Owing to its climatic relations,
moreover, virtually all the important crops of the
pedocalic zone are produced within its borders.
From north to south the region outlines a nearly
continuous belt of extensive grain fields flecked with
hay and pasture lands. In the north the Dakotas
envelope substantially the entire widespread areas
of major production of spring wheat, barley, rye,
flax and wild hay in the United States. 42 The southern Nebl'aska-central Kansas-central Oklahoma
section comprises the chief area of winter wheat
production.43 The western Oklahoma and northwestern Texas subdivision may be chiefly identified
with the sorghum center and two secondary cotton
centers.44 The southern end of the belt, from northwestern Texas to the West Gulf Coastal Plain, is the
only section without an important center.
The near unigenous crop character of the blackerths is, as previously stated, the converse of that
which might, without analysis, be anticipated on the
basis of their high !fertility, even when regarded
42 OJ. o. E. Baker: Graphic Summary of American Agriculture,
op. oit., pp. 439, 442, 443, 446, 450.
43 OJ, ibid., p. 440 •
.u OJ. ibid.} pp. 434, 445.
114
GEOGRAPHIC RELATIONSHIPS
apart from the climatic relationships. Such a contrary assumption would find fts origin in the general
but erroneous belief that the soil requirements of
most crops are not essentially different and that the
mere presence of large quanities of soluble constituents-the so-called fertilizers-represents the optimum soil conditions, a "fertile soil."
It is apparent, however, that the blackerths are
not well adapted nor adaptive to many crops, the limitations of these soils and the prairyerths being very
similar in this respect. Having evolved under grassland formations, the features they possess constitute
a reaction, adjustment, and unqualified adaptation
to this type of vegetation alone. Although the rela~
tion of normal pedalfers to the forest formations is
similar, the soils 0'£ this division are leached and
impovel'ished, and adapting their features to the
edaphic requirements of a given crop is a process
of supplementation and "building up" and not one
of removal and reduction-a modification virtually
impossible on any extended scale. Consequently,
the cereals, being botanically closely allied to the
grassland formation, and flax. and alfalfa, whose
growth habits are similar to the wild flaxes and
legumes growing intermingled with the natural
grasses, are the only crops of importance within the
region. As in the prairyerths, other crops whose
soil requirements are unlike those of the grassland
formation will grow in the region, but mostly through
tolerance or crop adaptation rather than voluntary
acquiescence. As a consequence, the region is almost one of crop homogeneity-grains and hay-the
AGRICULTURAL ADJUSTMENTS
115
fine, fibrous roots of these plants 45 finding the
granular soil most congenial.
The variety of grain in the different sections corresponds in its distribution with changes in temperature and slight changes in soil (page 65),
but the precise significant effect of each is unknown. The northern blackel'ths have the highest
content of organic matter and nitrates, tlie lime
layer is relatively shallow, and the soils are high
in soluble phosphates and potash. Accordingly, although the moisture supply is variable and indeterminate, the soils are in a position to offer the
four cool climate grains concentrated here every
pedologic advantage.
The inclusion of most of the extensive area of
wild or native hay production in the United States
in the northern blackel'ths is also noteworthy. The
leading plant associations are the tall needle grass
and slender wheat grass plant community, and the
short grama and western needle grass group. Both
these associations afford excellent grazing, have a
high carrying capacity,46 and produce the most nutritious and valuable native hay in the Great
Plains;n So nutritious are the grasses, in view of
the rich soils, that under prevailing economic conditions the necessity of planting cultivated grasses
extensively has apparently not yet arisen.
The soils of the winter wheat section are slightly
lighter in color, have a lower content of organic
Weaver: op. oit., pp. 133-179, 192-197.
Shantz: op. cit., pp. 94-95, 100-101.
47 Piper: Ilt al., op. cit., pp. 352-353.
45
46
116
GEOGRAPHIC RELATIONSHIPS
matter, and the carbonate zone is somewhat deeper
than the Dakota subgroup, but the general pedologic
relationships are essentially analogous. On the
other hand, the region has only one important grain
crop, wheat,48 but two forage crops, sorghum in the
drier central and western parts, and the long-rooted
alfalfa extending westward from the central prairyerths. The other small grains, though climatically
tolerant, occupy only minOT aCTeages.
The blackerths of the grain-sorghum belt of western Oklahoma and northwestern Texas aTe dark
brown rather than black in color, the subsoils are
reddish, and the carbonate zone is much more calcareous.40 The annual precipitation averages about
the same as that of the more northerly blackerths,
but evaporation is higher, in view of the increased
temperature, and the soil moisture is below the minimum required by the northern grains. Sorghum,
however, on account of its exceedingly well-developed root system,50 occupies the soil most thoroughly
and is capable of utilizing a much lower moisture
content. It is the typical low latitude blackerth
grain crop, various members of the millet-sorghumsudan grass group being extensively grown on the
blackerths of Africa and India.
The occurrence of several important minor centers of a non-graminaceous crop, cotton, in this district-the only crop of extra-regional significance
within the blackerths-is the most important excep48
H. C. Wallace, et al.: The Wheat Situation, Agriculture Year·
book, 1923, p. 97.
40
~o
C. F. Marbut: Soils of the Great Plains, op. oit., pp. 50-57.
Weaver. op. oit., p. 196.
AGRICULTURAL ADJUSTMENTS
117
tion to the prevailing grain-hay association. The
extension of the crop into this area is environmentally related in part to the fertile, unleached character of the soils and in part to the drouth-resistant
character, an attribute of this plant which is not
generally appreciated. Cotton is one of the more
xerophytic crops produced in the South, being capable of weathering low rainfall conditions for extended periods.
The southern end of the blackerth region is an
area composed chiefly of either immature and shallow soils (Edwards Plateau) or those underlain
with indurated carbonate zones (caliche).fi1 The
proportion of land in harvested crops is very low.
This section is in geneml pastoral rather than agricultural; it includes the greatest acreage of unimproved pasture in farms in the United States. 52 The
value of the pasture is not high, the prevailing plant
communities being mesquite and desert grass savannah with somewhat better pasturage-grama,
buffalo, and wire grass-in the Texas and Oklahoma
Panhandles. 58
The relationship of the Washington-Oregon blackerths to the Columbia Plateau wheat region is similar to that described jn the case 01£ the principal
blackerth belt. There is not the diversity of grains,
spring and winter wheat forming the two chief crops
of the region. 54
Marbut: op. cit., p. 53.
Ct. 0, E. Baker: A Graphic Summary of American Agriculture,
ap. cit., p. 425.
58 Shantz, op. cit., p. 83.
H Of. Baker: op. cit., pp. 438, 439.
51
52
118
GEOGRAPHIC RELATIONSHIPS
The unusual areal extent of most of the crop centers of the blackerths is reflective of the existence
of widespread bodies of essentially similar mature
soils, the Sandhill region of Nebraska and the
Texas-Oklahoma areas noted comprising the chief
exceptions. Such crop centers as developed, then,
were comparatively untrammeled. It is possible
that 'the limited area of mature soils in the southel'n
part of the belt may in time influence the l'ecent expansion of cotton growing in this district.
The Ohestnuterths.-The agriculture of the chestnuterths is a mere skeletal image od: the grain and
hay production of the blackerths-the western
fringe of a belt of peripheric agriculture. The
greater part of the region is pastoral. Outside the
irrigated valleys, such production as attains any
noteworthy importance is expressed only in minor
centers: (1) one of spring wheat in southwestern
South Dakota, (2) one of winter wheat on the high
tablelands of northeastern Colorado and adjacent
western Nebraska, (3) one of winter wheat and
barley in northwestern Kansas, and (4) one of forage sorghums, diffused but extensive, in western
Kansas and eastern Colorado. 55
The most important fundamental factor accounting for the agri-pastoral utility is obviously nonpedologic but climatic. The soils are slightly inferior to the blackerths-lighter in color, lower in
organic matter, and possessing a coarse, cloddy
structure-but the difference is immomentous in
comparison with the precipitation factor. In years
65
Ct.
ibiil,. pp. 32, 83, 36, 39.
AGRICULTURAL ADJUSTMENTS
119
of abnormal rainfall, the grain yields compare very
favorably with those of the more humid blackerths.
As in all pedocals, the pedologic consideration accounting for the agricultural features of the chestnuterths is their high fertility. It is this wealth
which the industry is capitalizing. But here, on account of the scanty water regime, the soils are near
Circean in character-attractive but hazardous.
Their riclmess in nutritive substances is a partial
compensation for the lower precipitation, owing to
its diminishing effects on the magnitude of the transspiTation coefficient; as a result, the more humid margins have been productive of secondary crop centers
drawn westward from the more humid blackerths.
The critical times are in the dry years, when Circe's
green fields turn brown; and hence the logical necessity of finding means whereby the rancher-farmer
can so manipulate his soils as to better take up and
preserve the rainfall.
The Browne'rths and Grayerths.-The prevailing
moisture supply of these groups is so low that practically none of the mature members is tilled. The
soils are adapted to xerophytic grasses, shrubs and
bushes, but domesticated forms of these vegetative
types are not cultivated.
Summary of Pedologic Relationships.-Summarizing the agricultural relationships of the two major
soil divisions, it appears that the impoverished
-pedalfers, though a handicap to man, are more serviceable than the unleached pedocals whose fundamental features, apart from the moisture content,
are essentially fixed and unalterable. With the gen-
120
GEOGRAPHIC RELATIONSHIPS
eral exception of the prairyerths, the pedalfers can
be amended to meet a diversity of crop requirements,
each soil group presenting somewhat different ecologic and economic conditions. The agricultural
response to these circumstances is exhibited in a
most extended crop variety including even important acreages of crops grown primarily in the pedocalie division. The comparative inelasticity of the
pedocals, on the other hand, narrows their crop
adaptivity to those whose edaphic relationships are
tolerant or adjustable to the soils' natural characteristics, chiefly the dry land members of the grass
family.
PASTORAL ADJUSTMENTS
DISTRIBUTION OF :PASTORALISM:
As the agricultural adjustments express themselves thl'oug'h cultivated crops, the pastoral industries signify their character through the natur'al
grassland formations and the domestic animals consuming this herbage. Where chief economic dependence rests upon tillage of the soil and the production of crops and forage, the adjustment may be
described as agricultural, although the area under
consideration may include bodies of pasture or
natural grazing land. Where the proportion of land
under cultivation is very small, however, and principal reliance is placed upon the natural range
rather than the field, the adjustment presents more
of the pastoral aspect.
PASTORAL ADJUSTMENTS
121
In the United States, the days of unbounded pasture, the purer pastoral type, passed with the opening of the 20th century, but its organization has
been taken by the more limited ranch which differs
but little in its fundamental geographic features
from its prototype of the unrestricted range. The
relationship is still one of stock, grass and water,
and supplementary feed where winter climate or
other exigencies demand the latter. Such feed may
be produced on minor acreages or the natural
grasses may be cut for hay, but the chief dependence rests upon the herd and its pasturage.
Pastoralism is, as far as the two major soil divisions are concerned, almost solely a pedocalic industry.56 While stock is allowed to run at large both
in forest and natural meadow throughout the pedalferic zone, the practice is in general confined to nonmature soils and is but incidental to agriculture.
Throughout the major part of their extent, however,
the pedocals are largely the home of flocks and herds
and their attendants. Only on their margins has
agriculture to any extent invaded and taken permanent possession of the area.
RELATIONSHIPS
Pastoralism, Grasslands and Soils.-The pursuit
of pastoralism is primarily dependent upon a single
environmental condition, the existence of great bod.
ies of natural grassland.
liS Cf. O. E. Baker: Agricultural Regions of North America (Map),
Economic Geography, Vol. II, No.4.
122
GEOGRAPHIC RELATIONSHIPS
The dependence upon extensive areas of natural
grasslands allocates pastoralism to a geographic
category somewhat different from that of agriculture. Agriculture '8 fundamental direct environmental interest is with soil and climate-a type of soil
and climate suited or adaptable to the production of
a selected plant. Pastoralism, on the other hand, is
but indirectly concerned with the soil and climate
giving rise to the plant life upon which its pursuance
depends. It accepts this life, moreover, virtually
status q~tO because the very conditions under which
pastoralism is carried on require it. (The reader
should here note that the term pastoralism is limited
to the utilization of natural grasslands; the "improved" or cultivated pasture husbanded by man is
in essence a phase of agriculture.) Soil and climate
are prime prerequisites to the existence of the vegetation but secondary factors in the prosecution of
the industry_
In seeking the relationships of soil to pastoralism,
therefore, one must look for them in the relationships of soil to grasslands. To what extent do the
two major soil divisions meet the requirements of
the grassland formations?
The Major Soil Divisions.-In view of their
genetic affiliations, it is a matter of course that the
pedocals should possess features more favorable to
the grassland formations. Having evolved under
the influence of grass and an arid climate, their
water balance is one which only grasses can tolerate,
and their characteristics aside from their moisture
content are naturally those most fully and uncondi-
PASTORAL ADJUSTMENTS
123
tionally adapted to this type of vegetation. Trees
will take root on them when encouraged and watered
by man, but their growth is not vigorous nor do they
possess the rugged healthful appearance of those
growing on normal mature pedalfers. Being alkaline in reaction and containing a high percentage of
soluble salts, there is too wide a discordance between their features and those of the soils occupied
by the forest formations under normal conditions. 57
The pedocals are fundamentally grassland soils.
The very opposite relations obtain in the pedalferic division. The normal mature pcdalfers are
most amiable to forest formations but of limited
adaptation to grasses. Grasses will grow on them,
but unless artifIcially preserved the areas in time
revert again to forest, as abandoned land and pasture problems everywhere testify, since the graminaceous is unable to maintain itself on the leached
acidic soils against the invasion of the more natural
type. In this soil division natural grasses are confined to certain immature or abnormal soils with
edaphic conditions unfavorable to forest associa~
tions.
Although the prevalence or grasslands in the
pedocalic zone is fundamentally a matter of the low
precipitation, owing to the influence of the latter
upon the soils' moisture content, it is patent that
the soils, aside from their moisture relation, are
also a basic factor in the maintenance and dominance of grasslands within t11eir area, and hence,
57 Cf. Tree Planting in the Great Plains Regions, U. S. Dept.
Agr., Farmers' Bull. 1312.
124
GEOGRAPHIC RELATIONSHIPS
except where the rainfall is adequate for agriculture, the region is largely utilized for pastoralism.
In so far as soils are essential to the growth of
grasses, the features of the pedocals are those
most favorable to the support and development of
this type of vegetation. Although primarily treeless
because of insufficient rainfall, these soils, even with
increased precipitation, wOll1d probably not be
adapted to the forest formations, as conditions in
the prairyerths so generally signify. In this region,
where the soils are very similar to the blackerths,
but the moisture content is adequate Ifor tree growth,
this type of vegetation has not extended into the
area except where the grassland soils have been
effaced by erosion (page 60). Only with the passage·
of time and advance into the new pedologic cycle
initiated by the increased rainfall, would the soils
develop the pedalferic features unqualifiedly favorable to forests. Compare in this connection the socalled degraded chernozems of Russia. 58
The normal pedalfers, being unfriendly to
grasses, naturally show the very opposite relationship to pastoralism. Maturity in this division
means the exit of grasslands. These soils, when not
demanded for agriculture, are the normal forest and
nemoriculturallands (see below),
The Great Soil Groups.-Each of the great soil
groups marks a general variation in quality and
quantity of pasturage and in degree and character
of utilization, the ohange corresponding with differences in rainfall and soils. Unit for unit the pas68
Glinka;
op. o't., pp. 89 ft.
PASTORAL ADJUSTMENTS
125
turage declines from blackerths to grayerths with
respect to both quality and carrying capacity but
conversely with regard to degree of utilization.59
The grayerths and brownerths, with the poorer soil,
lower precipitation and inferior pasturage, are es~
sentially purely pastoral, and are largely utilized for
sheep,~Q particularly those sections suited for winter
range only.61 The chestnuterths, with better soil
and climate, are both agricultural and pastoral, but
the former is chiefly restricted to the several eenters
previously mentioned along its more humid margins,
and range land predominates. Comparatively large
boaies within the blackerths, especially in the southern and western parts of the belt, may also be included in this category.62 In both these regions, because the quality of the pasture is high, cattle predominate, although sheep are also conunon.
Throughout all these regions, but especially in the
grayerth and brownerth belt, transhumance is common, the highlands within them, in accordance with
the laws of the vertical distribution of soils, having
belts of better and more humid soils supporting pasture grasses of higher quality.
59 Of. E. W. Sheets, et a!.: Our Beef Supply, Agr. Yearbook, 1921,
pp. 252-253; Shantz, op. oit.
60 Cf. D. A. Speneer, et al.: The Sheep Industry, Agr. Yearbook,
1921, p. 254.
61 Sheets, et al.: op. cit., p. 253.
62 Cf. Baker: op. cit., p. 425.
126
GEOGRAPHIC RELATIONSHIPS
NEMORICULTURAL ADJUSTMENTS
DISTRIBUTION OF NEMORICULTURE
This type of adjustment refers to those pursuits
of man in which his activities are .founded upon the
utilization of nemoral, or forest, vegetation in contrast to pastoralism and grasslands. Though expressed in various forms, lumbering is the only
branch of major importance in the United States,
the production of other forest commodities, such as
tannin, turpentine, resin, etc., being relatively insignificant.
Based primarily upon the forest formation, lumbering is almost wholly confined to that soil division
whose dominant vegetation is made up of forest associations,l1s the pedalfers. Beginning with the graybrownerths of the New England province, the industry gradually spread westward and northward to
the podsols, southward through the central graybrownerths to the red-and-yellowerths and ferruginous laterites of the South, and then westward and
northward again to the pedalferic groups of the
Rocky Mountain and Pacific Mountain systems.
Although carried on to some extent in all these
soil regions, the areas of major production, as is
well known, are in the Gulf and Pacific states. 64
The balance of the country, outside the Rocky Mountains, has in general been cut over. The cut-over
03 Cf. R. V. Reynolds and A. H. Pierson: Lumber Cut of the
United States, 1870-1920, U. S. Dept. Agr., Bull. 1119, p. 12.
6~ Yearbook of Agriculture, 1927, p. 1200.
NEMORICULTURAL ADJUSTMENTS
127
area still produces a fairly large aggregate but the
output is chiefly derived from the non-mature soils.
RELATIONSHIPS
The Major Soil Divisions.-In seeking the pedo·
logical relationships between the major soil divisions and lumbering, the fact that the areas of distribution of natural forests and the normal pedalfers are essentjally mutually inclusive 65 is of prime
significance in indicating the fundamental ecological
relations between the two. GO These soils, having adjusted their features to an arboreal cover, are naturally Ifully attempered to this type of vegetation, and
are not adapted without modification to the grassland formations. The climate is friendly to grasses,
as the former numerous natural glades and grasslands scattered throughout the eastern part of the
United States signify-the Hempstead (Long Island) prairie, the Black Belt of Alabama, the" oak
openings" of Wisconsin and Michigan, the grasslands of Kentucky, the prairies of Iowa, etc.-but
the mature soils of the region and most of the nonmature members are in some measure unsuited to
their requirements. The grasses seem intolerant of
the leached non-calciferous nature of the soils. But
the edaphic relationships of trees being diametrically opposite to those of grasses, forests find the
acidic light colored soils, with their continuous
Cf. Reynolds and Pierson, op. oit.
J. Kittredge, Jr.: The Uso of Soil Surveys in Forestry, Proc.
and Papers First Int'l. Congo Soil SeL, Com. V, p. 562.
65
66
128
GEOGRAPHIC RELATIONSHIPS
downward movement of water carrying soluble constituents to great depths, fully congenia1. G7
As in the case of the grasslands and pedocals, the
relation of soil water to precipitation gives climate
a basic position in the ecology of forests, but its situation is not determinative, as the absence of forests
on the prairyerths and many small glades throughout the zone indicate. Since the water content of
these soils is in general as high as in the normal
pedalfers, it is apparent that the pedologic are more
important than the climatic conditions. Until the
soils have become more or less acid, they seem to
resist the general advance of the forest formations,
although the climate is favorable to their growth.
The Great Soil Groups.-Referring to the great
soil groups for variations within the major division,
the broad consociation of certain forest associations
and aspects of lumbering with a given soil group is
noteworthy. Each soil region, with its soils fundamentally unlike those of its associate regions, presents 'Pedologic conditions, forest associations, and
economic circumstances more or less contrastive
with those of the other great soil groups.6S
If any of the great soil groups may be designated
as largely nemoricultural with regard to past as well
as future utilization, the podsols deserve that consideration. These leached acid soils are poor for
agriculture but admirably adapted to pines, spruce
and hemlock, as the former magnificent stands of
61 Of. C. G. Bates: The Special Problems of Forest Soils, Proc.
and Papers First Int'!. Congo Soil Sci., Com. V, pp. 566-574.
008 Of. Kittredge: op. cit., p. 563.
NEMORlCULTURAL ADJUSTMENTS
129
this forest association fully signify, Here the lumberman reigns supreme and he is furthermore likely
in the ,future, following reforestation or develop~
ment of the second growth, to maintain this supremacy. Having acquired their features under the
influence of the northern coniferous forest, and
being the least suited of the great groups for agriculture, the more basic economic use of the podsols
is that of lumber production.
The normal eastern gray-brownerths stand virtually at the opposite extreme. Their most economio
fundamental utility is agriculture. Although particularly adapted to hardwoods and originally covered
with an extended variety of their associations (compare their present crop diversity), they comprise the
most valuable of the light colored pedalfers for
agriculture. Following the opening of the Middle
West for settlement, they were !'apidly cleared for
farms and practically none of their areas is left for
timber, not even second growth. Nor are they
likely, on account of their high agricultural worth,
to be reforested.
The red-and-yellowerths, the leading eastern lumbering soils, are intermediate in certain respects be~
tween the gray-brownerths and the podsols. They
might be described as agri-nemoricultural soilsbetter utilized in part for agriculture and in large
part for forestry. Certain areas are essential and
desirable for the production of crops, especially those
climatically restricted to the area. But there are
large bodies of these leached soils better maintained
in forests. Their general agricultural improvement,
130
GEOGRAPHIC RELATIONSHIPS
in view of the vastly superior possibilities inherent
in the gray-brownerths and othe:r soil groups, is at
present uneconomic. The red-and-yellowerths are
primarily suited, because of their genetic alliances,
to the valuable southern yellow pine and oak-pine
associations. Although much of their enormous
stand of this growth has been cut, extensive reforestation programs are also under way. 'With the long
growing season and abundant precipitation, the region is OIle of the most profitable areas for the production of softwoods in the United States.
The general relationships of the ferruginous laterites are similar in part to the red-and-yellowerths
and in 'Part to th~ podsols. Being leach~d to a high
degree and prevailingly sandy, the mature soils of
this region are less adapted to agriculture than the
red-and-yellowerths, although economically suited
to a limited number of crops. Though not preferably nemoricultural to the same extent as the podsols, the largest proportion of the mature '!ferruginous laterites are better utilized for timber production.
The nemoricultural and soil relations of the western pedalfers differ in no important essentials from
those of their corresponding eastern groups. As
economic conditions warrant, the more valuable
gray-brownerths are being cleared and retained in
agricultural service, whereas the less valuable cutover rederths not employed for fruit production are
gradually being rerorested or abandoned to second
growth.
SUMMARY AND OONCLUSION
Such relationships as have been noted in this survey bring out the fact that the United States possesses two major soil divisions of markedly unlike
character and geographic significance. One of these
divisions, as a whole, is naturally relatively poor
and of low fertility; the other is comparatively rich
and of high fertility. The poorer division, the pedalferic, is the leading agricultural soil and one of great
crop diversity in spite of its natural impoverishment, whereas the rich division, the pedocalic, is the
principal pastoral soil with only peripheral agricultural adjustments of neal' unigenous character.
Pedologically, the productiveness of the pedalfers,
aside from the prairyerths, is related largely to the
fundamental physical constitution of the mature
soils. In view of their structure and high moisture
content, the soils are able to utilize such chemical
elements as may be applied to them artificially, and
they are responsive to crop rotations and mechanical
manipulation. The great crop variety of the soils
is a reflection of their marked plasticity. Being
more or less impoverished, they can be built up to
meet a diversity of crop requirements, limited only
by climatic conditions, in contrast to the unleached
pedocals whose crop range, owing to their almost
131
132
SUMMARY AND CONCLUSION
inflexible features, is quite restricted. Although the
restrictive character of the pedocals is to a great
ex.tent due to the soils' low water balance, it may
also be identified with the soils' non-hydric attributes. The latter are fully congenial chiefly to
Gramineae only. The conclusion is particularly
warranted, aside from the fact that in the course of
their evolution the soils have adjusted their features
to this type of vegetation by (1) comparisons with
the prairyerths, whose non-hydric features are very
similar to the blackerths and whose moisture supply
is as abundant as that of the normal pedalfers, but
whose crop adaptivity is equally limited, and (2) the
virtual absence of any other types of crops on the
more humid pedocalic margins where moisture conditions would favor their production.
On the other hand, the decreasing westward supply of moisture in the pedocals curtails the production of even graminaceous crops and forces the area
back upon its own grassland formations and pastoralism. Having evolved under the influence of
grasses, the soils, unlike the normal pedalfers, are
fully attuned to meet the edaphic requirements of
this type of vegetation only.
In the pedalferic zone, the natural vegetation is
the forest formation, but tree growth, albeit the
moisture supply is adequate throughout the region,
is limited to the normal mature and immature light
colored pedalfers, as only their features are adapted
to the arboreal associations. These soils are there~
fore the natural seat of nemoriculture but the
SUMMARY AND CONCLUSION
133
actual pursuit of forest industries is governed more
by economic than environmental conditions, although in the long run tending to be restricted to
the poorer of the great soil groups, such as the pod~
sols and extensive areas in the red-and-yellowerth
regions.
Regarded in a broad way, either with respect to
the major soil divisions or their great groups, it is
evident that the problems of the various regions occupied by these soils are strikingly different in so
far as they are related to the character of their soils.
The type of thinking in the way of policies or programs required in the case of one may be wholly Ulllike that demanded by another. Unfortunately,
however, this has generally not been the case, as is
abundantly illustrated by innumerable :popular, as
well as scientific, treatises which concern themselves
with pedologic phenomena. Geographers, geologists, agronomists and others interested in this aspect of the natural environment have in general not
recognized such differences. Local facts have only
too often been given a regional interpretation.
With increasing and more widespread knowledge
of the real nature of the soil and its relative importance, such difficulties as have just been suggested
will tend to disappear. Pedology is one of the
younger sciences; its point of view and the true
significance of its phenomena are as yet not generally understood and appreciated. It is hoped that
the concepts outlined in this work may assist in
bringing about a fuller comprehension of the
134:
SUMMARY AND CONOLUSION
soils of th<! Unite'd States as a whole and some of
their significant relationships to human activities.
Though manifestly incomplete, the study may serve
to open further the vast, almost untouched, field of
soil geography.
BIBLIOGRAPHY
( General)
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These reports constitute most excellent and original detailed
matorial on the soils and geography of the United States. They
have been used as the chief source of facts in this study. Most
of the reports are issued by counties, each of which contains a
section describing the area, its climate, agriculture and soils.
They have not been itemized under the special bibliography below
owing to the very large number of reports involved.
2. N. M. FENNEM..I.N: Physiogra.phic Divisions of the United
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3. D. K. GLINKA: Die Typen del' Bodenkunden, Berlin, 1914.
4. H. HARRASSOWITZ: Laterit, Berlin, Gebriider Borntrager,
1926.
5. J. B. KrNCER: Atlas of Ameriean Agriculture, Part II,
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6. C. F. MARBUT: A Scheme for Soil Classification, Proc. and
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7. - - : Outline of a Scheme for the Differentiation of Soils
into Mapping Units on a UnifOl'In Basis for all Countries, Proc.
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Special Sessions, 1927, pp. 259-268.
8. - - : The Contribution of Soil Surveys to Soil Science,
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9. - - and C. B. MANIFOLD: The Soil of the Amazon Basin
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1926, pp. 414-442.
135
136
BIBLIOGRAPHY
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11. E. RAMANN: The Evolution and Classification of Soils,
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12. REPORT OF COMMITTEE ON 1'ERMINOLOGY, Soil Terminology,
Amer. Soil Survey Assn., Bull. IX, 1928, pp. 28-58.
13. J. C. RUSSEJ,L: Forms of Soil Structure, Amor. Soil Survey Assn., Bull, X, 1929, pp. 120-133.
14. H. L. SHANTZ and C. F. MARBUT: The Vegetation and
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1923.
15, - - and R. ZON: Natural Vegetation, Atlas of .Amer,
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16. C. F. SHAW: A UniIorm International System of Soil
Nomenclature, Proc. and Papers ]!'irst Int'I. Congo Soil Sd.,
Com. V, 1927, pp. 32-37.
17. A. P. UPSON: Soil Fertility, Soil Exhaustion and Their
Historical Significance, Quarterly Jour. Eeon., Vol. XXXVII,
No.3, 1923, pp. 385-411.
18. D. VILENSKY: The Classification of Soils on the Basis of
Analogous Series in Soil Formation, Proc. Int'l. Soc. Soil ScL,
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19. R. D. WARD: The Climates of the United States, New
York, Ginn & Co., 1925.
20. S. A. ZAKHOROV: Achievements of Russian Science in
Morphology of Soils, Russian Pedological Investigations II,
Leningrad, Academy of Sciences, 1927.
(Pedalfers)
21. M. BALDWIN: Some Characteristic Profiles in tlle North
Central States, Amer. Soil Survey Assn., Bull. VII, Vol. I,
1926, pp. 122-128.
22. - - : The Gray-Brown Podsolic Soils of Eastern United
States, Proc. nnd Papers First Int'l. Congo Soil Sci., Com. V,
1927, pp. 276-282.
23. H. H. BENNETT: The Soil and Agriculture of the Southern
States, New York, Macmillan Co, 1921.
BIBLIOGRAPHY
137
24. - - and R. V. A.LLISON: The Soils of Cuba, Washington, D. C., Tropical Plant Research Foundation, 1928.
25. P. E. BROWN and T. H. BENTON: Microorganisms in Some
Soil Profiles in Iowa, Proc. and Papers First Int'l. Congo Soil
Sci., Com. III, 1927, pp. 100-106.
26. E. D. FOWLER: Iron A.ccumulation in Soils of the Coastal
Plain of the Southeastern United States, Proe. and Papers First
Int'!. Congo Soil Sci., Com. V, 1927, pp. 435-441.
27. - - : Profile Characteristics of SOIDe Coastal Plain Soils,
Am. Soil Survey Assn., Bull. VI, Vol. I, 1925, pp. 19-23.
28. L. C. GRAY and OTHERS: Utilization of Our Lands fox
Crops, Pasture and Forests, U. S. Dept. Agr., Agriculture
Yearbook, 1923, pp. 415-506.
29. W. E. HEARN: Southern Soils, Amer. Soil Survey Assn.,
Bull. VII, Vol. I, pp. 15-24A.
30. H. H. KRUSEKOPF: The Brown Soils of the Norih Central States, Amer. Soil Survey Assn., Bull. VI, Vol. II, 1925,
pp. 146-148.
31. SOIL SURVEY REPORTS, University of Illinoi,9, Agricultural
Experiment Stations.
32. J. O. VEATCH: Northern Podsol Soils in the United Stated,
Amer. Soil Survey Assn., Bull. VI, Vol. I, 1925, pp. 24-2SA.
33. - - : Profiles of Soils in the Great Lakes Region of the
United States, Proe. and Papers First Int'l. Congo Soil Sci.,
Com. V, 1927, pp. 350-357.
34. A. R. WHITSON: Soils of Wisconsin, Wis. Geol. and Nat.
Hist. Survey, Bull. No. 68) Soil Series 49) 1927.
(Pedocals)
35. F. A. HAYEs: Revision of the Grundy Series or Nebraska,
Amer. Soil Survey Assn.; Bull. IX, 1928, pp. 86.A-99.
36. M. H. LATHAM: Some Profiles of Representative Western
Soils, Amer. Soil Survey Assn., Bull. VII, Vol. I, pp. 25-42A.
37. - - : Some Western Problems in Soil Classification and
Mapping, Amer. Soil Survey Assn., Bull. VI, Vol. I, 1925,
pp.48-54.
138
BIBLIOGRAPHY
38. C. F. MARBUT: Soils of the Great Plains, Annals Assn.
Amer. Geogrs., Vol. XIII, No.2, 1923.
39. T. D. RICE: Profile Studies or Representative Soils in the
Northern Prairie States, Amer. Soil Survey Assn., Bull. VII,
Vol. I, 1926, pp. 1-14A.
40. J. C. RUSSELL and E. B. ENGLE: Soil Horizons in the
Central Prairies, Amer. Soil Survey Assn., Bull. VI, Vol. I,
1925, pp. 1-18.
41. - - - - : The Organic Matter Content and Color of
Soils in the Central Grassland States, Proc. and Papers First
Int'L Congo Soil Sci., Com. V, 1927, pp. 343-349.
(Geographic Adjustments)
42. A. M. AGELASTO and OTHERS: The Cotton Situation, U.
S. Dept. Agr., Yel1.rbook, 1921, pp. 323--406.
43. O. E. BAKER: A Graphic Summary of American Agriculture, U. S. Dept. Agr., Yearbook, 1921, pp. 407-506; Agricultural
Maps, U. S. Dept. of Agr., Yearbook of Agriculture, 1928, pp.
640-665.
44. - - : Agricultural Regions of North America, Economic
Geography, Vol. II, No.4, pp. 459-493; Vol. III, No.1, pp.
50-86; Vol. III, No.3, pp. 309-339; Vol. III, No.4, pp. 447465; Vol. IV, No.1, pp. 44-73; Vol. IV, No.4, pp. 399-433;
Vol. V, No. I, pp. 36-69.
45. C. R. BALL and OTHERS: Oats, Barley, Rye, Rice, Grain
Sorghums, Seed Flax and Buckwheat, U. S. Dept. Agr., Yearbook, 1922, pp. 469-568.
46. C. G. BNI.'ES: The Special Problems of Forest Soils, Proe.
and Papers First Int'I. Congo Soil Sci., Com. V, 1927, pp.
566-574.
47. H. H. BENNE~'T: The Geographical Relation of Soil Erosion to Land Productivity, Geogr. Rev., Vol. XVIII, 1928,
pp. 579-605.
48. W. B. GREELEY and OTHERS: Timber: Mino or Crop?,
U. S. Dept. Agr., Yearbook, 1922, pp. 83-180.
49. S. P. KRAVKOV: Achievements of Russian Science in the
BIBLIOGRAPHY
139
]i'ield of Agricultural Pedology, Russian Pedological Investigations IX, Leningrad, Academy of Sciellces, 1927.
50. C. H. KYLE: Growing Corn in the Southeastern States,
U. S. Dept. Agr., Farmers' Bulletin 1149.
51. C. F. MARBUT: The Rise, Decline and Revival of MaltllUsianism in R,elation to Geography and Character of Soils, Annals
Assn. ArneI'. Geogrs., Vol. XV, 1925, pp. 1-25.
52. C. V. PIPER and OTHERS: Our Forage Resources, U. S.
Dept. Agr., Agriculture Yearbook, 1923, pp. 311-414.
53. H. L. SHANTZ: The Natural Vegetation of the Great
Plains, Annals Assn. Amer. Geogrs., Vol. XIII, No.2, 1923,
pp. 81-107.
54. J. R. SMI~'H: Industrial and Commercial Geography,
New York, Hemy Holt & Co., 1925.
55. - - : North America, New York, Harcourt, Brace & Co.,
1925.
56. - - : Tree Crops, New York, Harcourt, Brace & Co.,
1929.
57. UNITED STATES CENSUS OF AGRICULTURE, 1925, Parts I-III.
58. E. D. VOSDURY and T. R. ROBINSON: Culture of Citrus
Fruits in the Gulf States, U. S. Dept. Agr., Farmers' Bull. 1343.
59. J. E. WEAVER: Root Development of Field Crops, New
York, McGraw-Hill Book Co" 1926.
60. J. W. WESTON and OTHERS: The Agriculture of the Upper Peninsula, Mich. Agr. Exp. Sta" Special Bull. 116, ]922.
61. R. ZON: Silviculture as a Factor in Maintaining the Fertility of Forest Soils, Proc. and Papers First Int'l. Congo Soil
Sci., Com. V, 1927, pp. 575-582.
INDEX
A
Agricultural adjustments, 80-120
pedalfers
land under cultivation, 86-98
principal crops, 98-120
pedocals
land under cultivation, 88,
92-94
principal c r 0 p s, 100"'101,
112-119
Alabama, 90
Alkalies and alkaline eartns
ferruginous laterites, 26
gray-brownertbs, 23
pedalfers, 46, 41
pedocals, 10, 71
podsols, 21
Alluvial fans, 66
Alumina
gray-brownertbs, 22
non-lime-accumulating Boils, 15
pedalfers, 46, 41
pedocala, 72
podsols, 20
Appalachian Plateau, 20, 24, 50
Areal correlations, 81-82
Mid soils, 63
Arkansas, 90
Attributive system, 9-16
B
Blackcrtbs
as sub-bumid Boils, 64
crops, 112-118
Blackertbs
description, 28-29
distribution, 28
evaluation, 29, 91, 112-118, 125
land under cultivation, 91
natural vegetation, 65-66
pastoralism, 124-125
Russian, 1
Brownerths
as sub-arid soils, 64
crops, 119
description, 30--31
distribution, 27-28
evaluation, 97, 98, 119, 125
land under cultivation, 97
natural vegetation, 66
pastoralism, 125
C
California. Trough, 61, 79
Chemical characteristics
lime-accumulating soils, 14
non-lime-accumulating soils, 14
Chemical classes, 14-16
Chemical profile
advantages of, 73
disadvantages of, 48-49
pedalfers, 45-49
pedocals, 69-74
Chestnuterths
as semi-acid Boils, 64
crops, 118-119
description, 29-30
distribution, 27-28
143
144
INDEX
Chestnuterths
evaluation, 30, 97-98, 118-119,
125
land under cultivation, 97
natural vogetation, 66
pastoralism, 125
Chromatic classes, 9-10
Chromatic names, 17, 18
Classification
attributive, 2, 9-16
botanic, 8
chemical, 14--15
chromatic, 9-10
climatic, 2, 7-8
criteria, 1-3
genetic, 2, 3-8
geographic, 2-3
geologic, 2, 4.-7
maturatal, 11-13
problem of, 1-2
soil series, 1
textural, 10-11
topographie, 8
Climate
relation to soil evolution, 34-38,
44-45, 57, 58-59, 63-65,
68-72
relation to Boil use, 83-86
soil groups, 7-8
Coastal Plain
parent materials, 6
soils, 6, 24-25, 27, 41, 50, 107,
110, 113
Color profile
blackerths, 28
brownerths, 30
chestnuterths, 29-30
ferruginou!l laterites, 25
gray-browne:rths, 22
grayerths, 31
pedalfers, 56-57
pedQcals, 77-79
Color profile
podsols, 20
prairyerths, 27
red-and-yellowertha, 24
significance of, 55-56
Colorado, 31, 118
Colors, soil, 9-10, 17-18, 55-57,
77-79
Columbia Plateau, 117
ClOp centers and great soil
groups, 99-100, 106-107
alfalfa, 105, 114
apples, 105
barley, 105, 113, 115
beans, field, 106
citrus fruitB, III
clover, 105
corn, 102, 103, 104, 105, 108,
109-110
cotton, 105, 108, 109, 110, 113,
116-117
flax, 113-114
hay, 105, 113, 114, 115
oats, 103, 105
peanuts, 108, 110
potatoes, Ill, 112
rice, 108
rye, 105, 113, 115
sorghum, 113, 116, 118
sugar beots, 106
sugar cane, 108
timothy, 105
tobacco, 105, 108, 109, 110
vegetables, 111
wheat, 105, 113, 115, 116, 117,
118
Crops, principal
areal correlations, 99-100
pedalfers, 100, 102-112
pedocala, 100-101, 112-119
Crystalline rocks, 6, 40, 66
Cuba, 55
INDEX
Cultivated lanc1pedaliers, great Boil groups,
94.-98
major soil divisions, 87-92
pedocals, great soil groups, 9798
major soil divisions, 88, 92f>4
D
Dakotas, 10, 104, 113, 116, 118
Diversity of soils, 1, 5-6, 16-18,
40
E
Eluviation, 45
Eolian soils, 5
F
Fauna, soil, 42
Fertilization, relation to
structure, 54, 89-90
texture profile, 90-91
Florida, 28, 43, 111
Forest
as factor in soil evolution, 35
industries, 126-130
soils, 8, 18-26, 53, 94-97, 105112, 126-130
G
Genetic system, 3-8
Geographic relationships, 80-134
agricultural adjustments, 86120
general principles, 86-86
nemoricultural
adjustments,
126-130
pastoral adjustments, 120-125
Geology and soils, 4
discordance, 5-7
Georgia, 25, 33, 90, 104, 110
Glacial Boils, 6, 40, 66
145
Grassland
as factor in soil evolution, 35,
69
soil and pastoralism, 121-125
soils, 8, 26-31, 65-66, 97-98,
102-105, 112-119, 120-125
Gray-brownerths,18
climate, 37, 38
crops, 105-10B
description, 21-23
distribution, 19, 21
evaluation, 23-24, 95, 96, 105107, 129, 130
forest industries, 129
land under cultivation, 96, 96
naturill vegetation, 39
nemoriculture, 129
Grayel'ths
as arid soils, 64
crops, 119
description, 31
distribution, 27-28
evaluation, 97, 98, 119, 125
land under cultivation, 97
natural vegetation, 66
pastoralism, 125
Great Plains, 10, 19, 79
Great soil groups
crops, principal, 101-119
description, 18-31
forest industries, 128-130
land under cultivation, 94.-98
pastoralism, 124.-125
relative l'auk, 95
Groups (see, classification, great
soil groups major soil divislons)
H
Hardpans, 13, 31, 96, 110
Hill country soils, 41
146
INDEX
Horizons, definitioIls of
A, 21, 45
B, 21, 45
C,48
Hum!Ln !Lctivities and Boils, 80
Humid soils 36, 63
I
Igneous rocks, 40
Indiana, 103
Intermontane Plateau, 21, 79
Iowa, 43, 104
Iron
gray-hl'(}wnerths, 22
non-lime-accumulating soils, Hi
peduliol's, 16, 47
pedocals, 72
PQdsols, 20
K
Kansas, 105, 113, 118
Kentucky, 107
L
Lacustrine Boils, 40, 66
Lake states, 6, 50, 107, 112
Land forms (see topography)
Laterites, ferruginous, 18
climate, 37
crops, 110-111
description, 25-26
distributioIl, 19, 25
evaluation, 26, 95, 96, 110-111,
130
forest industries, 130
land under cultivation, 95, 96
natural vegetation, 39
;nemoriculture, 130
Limo-accumulating soils
(see
pedocals)
definition, 14
distribution, 16
nomenclature, 16
relation to purent materials,
66-67
Lime zone
blackerths, 29
brownerths, 30
chestnutm-ths, 30
grl1yerths, 31
lime-accumulating soils, 14
non-limo-accunmlating soils, 14
pedaliers, 16-48
p<ldoca.ls, 70-72
prairyortlls, 59, 60
Limestone soils, 4, 5, 7, 40, 66
LOl)sllial so)'1$, 5-6, 40, 66
LouiSiana, 90
M
Maine, 43, 112
Major Boil divisions
crops, principal
pedalfers, 100, 102-112
podocals, 100-101, 112-119
cultivated land
podalfel's, 87-88
peilocu.1s, 88
relation to cultivatod land
pedaHers, 88-92, 94-97
pedocals, 92-94, 97-98
Marl soils, 66
Maryland, 104
Maturatal claBsea, 11-13
Mature soils
characteristics, 11-12, 14
relation to topography, 11-12,
41-42
relatiV'o proportion, 41-42, 62
significance, 15, 19
147
INDEX
Metamorphic rocks, 40
Michigan, 106, 112
Micro-flora, 42
Micro-organisms, 42-43
Minnesota, 107, 112
Mississippi, 5, 90
Mountain soils, 21, al-3ll
N
Natural vegetation
pedal£ers, 38-39
Iledocals, 65-66
relation to soil evolution, 4445, 48-49, 69
relation to soil use, 82, 83-86
Nebraska, 43, 103, 104, 113, 118
N emoricultural adjustments
distribution, 126-127
l'elationships, 127-130
Nevada, 70
New England, 20, 43
New York, 20, 43, 107
Non-lime-accumulating soils (soe
pedal:fers)
definition, 14-15
distribution, 16
nomenclature, 16
relation to parent materials, 40
Normal soils, 10, 14
North Carolina, 42, 43, 109
Number of soils, 1
o
Ohio, 10, 43, 104
Oklahoma, 113, 116, 117, 118
Oregon, 117
Organic matter
blackerths, 28
chestnutel'ths, 30
gray-brownerths, 22, 23
pedalfors, 48-49
Organic matter
pedocals, 72-73
podsoIa, 20
red-and-yellowerths, 24
P
Pacific Coast, 36, 19
Parent material
pedaliel'ic, 39-41
pedocalic, 66-67
relatioll to soil evolution, 5-7,
35, 40-41, 66-67
Pastoral adjustments
distribution, 120-121
relatiollship, 121-125
Pedal£ors
agricultural adjustments
crops, principal, 98-120
land under cultivation, 86-98
characteristics, evaluated
advantageous, 51-52, 54-55,
56
disadvantageous, 44, 48-49,
50-51, 54
chemical analysis, 47
crops, principal, 100-101, 112119
definition, 16
description
cllemical properties, 44-49
physical properties, 49-59
distribution, 34
diversity of crops, 100, 101-112,
120, 129, 131
economic reactions, evaluated
favorable, 89-91, 96
limited, 88-S9, 91, 96-97
environment
climate, 35-38
land forms, 41-42
micro-ilora, 42
148
INDEX
Pedalfers
environment
natural vegetation, 38-39
parent material, 39-41
Boil fauna, 42
forest industries, 126-130
great Boil groups, 18-27
land under cultivation
proportion of, 87-88, 95-97
relationship to, 88-92
natural grasses, 26, 59-61, 123,
127
adjustments,
nemoricultural
126-130
pastoral adjustmonts, 121-125
profile
chemical, 45-49
color, 56-57
structure, 52-53
texture, 50-52
Pedocals
agl'icultural adjustments
crops, principal, 100-102,
112-119
land under eultivation, 88,
92-94, 97-98
characteristics, evaluated
advantageous, 18-74, 7{-75,
75-76, 92-93
diaadvantageous, 76, 92
cheJDical analysis, 71
crops, principal, 100-101, 112-
119
definition, 16
description
chemical properties, 68-74
physical properties, 74--79
distribution, 63, 65
economic reactions, evaluated
favorable, 93-94, 97
limited, 92, 97
envilonment, 63-67
J?edocals
environment
climate, 63-65
land forms, 67
natunt] vegetation, 65-66
parent material, 66-67
forest industries, 126
great soil groups, 27-31
land under cultivation
proportion of, 88
relationships, 92-94, 97-98
minor belts, 79
nemoricultural
adjustments,
126
pastoral adjustments, 121-125
proflle
ch.emical, 69-74
color, 77-79
structure, 75-71
texture, 74-75
tree growth, 123, 124
uniformity of crops, 100, 113115, 131-132
Pedologic cycle, 11
Piedmont soils, 6, 24, 110
Plain soils, 41
Plateau BoilS, 21, 4:1
Podsolll, 18
climate, 37
crops, 112
description, 20-21
distribution, 19, 20
cvaluatjoll, 21, 95, 96-97, 112,
128-129
forest industries, 126, 128-129
land unde:r cultivation, 95, 9697
natural vegetation, 39
Prairyerths, 18
elimate, 58
contrast with light colored
pedaHers, 57-58
149
INDEX
Prairyerths
crops, 102-105
doscription, 26-27
distribution, 19
environment, 58-60
evaluation, 27, 58, 61, 95, 96,
102-105
land under cultivation, 95, 96
rolation to pedalfers, 60-61
relation to prairie grasses, 5960
'Profile, definition, 11
Puget Trough soils, 61, 107
R
Red-and·yellowerths, 18
climate, 37
crops, 108-110
description, 24
distribution, 19, 24
evaluation, 25, 95, 96
forest industries, 108-110, 126,
129-130
land under cultivation, 95, 96
lime, 24
natural vegetation, 39
Relationship factors
areal correlations, 81-82
associate elements, 83-86
primary adjustments, 81
Residual aoils, 5, 6, 40
Rocky Mountain System, 2:1
Rough broken land, 32-33
s
Sandstone soils, 4, 5, 7, 40
Sedimentary rocks, 39-40
Semi-arid soila, 63, 64:
Series, soil, 1, 41
Shale Boils, 40, 66
Soil seience and botany, 8
climatology, 7-8
geology, 4-7
phySiography, 8
Solum, 14
&luth Carolina, no
Structure
blackerths, 28, 29
brownerths, 31
chestnuterths, 30
economic significance of, 53-54,
89-90
ferruginous laterites, 25
gray-brownerths, 22, 23
grayerths, 31
pedalfers, 52-53
pedocals, 75-77
podsols, 21
:red-and-yellowerths, 25
Structure profile
evaluation of, 53-55
pedalfers, 52-53
pedocals, 75-77
Sub-arid Boils, 64
Sub·humid soils, 64
T
Tennessee, 6, 104
Texas, 27, 90, 113, 116, 117, 118
Textural classes, 10-11
Texture
significance of 1Q-11, 107
Texture profile
advantages of, 50-51, 90-91
disadvantages of, 51-52
pedalferic, 50-52
pedocaIic, 74-75
Till PlainS, 10, 41
Topography
pedalfers, 41-42
INDEX
150
Topography
pedocals, 67
relation to soil evolution, 1113, 19-20, 31, 35, 67
relation to Boil use, 83-861 8687
Transported soils, 5, 6
Types, Boil (Bec classification)
u
Upland soils, 8
Upper Lakes Region, 20
V
Valley and Ridge Province, 24
W
Walla Walla Plateau, 79
Washington, 117
West Virginia, 20
y
Young Boils, 12, 61, 104, 107,
110, 117, 123, 127